Bloo - Mac's 7-year-old imaginary friend and best friend who resembles a simple domed cylinder. Bloo is sometimes self-centered and narcissistic almost to the point of psychotic delusion and has a knack for getting into trouble. However, he still has a good heart and apologizes for his actions. Bloo loves paddleballs even though he can't make the ball hit the paddle (though the only time he was able to do it was in the episode "Let Your Hare Down"). His full name is "Blooregard Q. Kazoo". He has become increasingly more mischievous over the run over the series and is shown to have bad memory some of the time. He is voiced by Keith Ferguson.
Mac - A bright and somewhat shy 9-year-old boy who visits Foster's. He almost always seems to know what to do when there is a problem. Mac becomes extremely hyperactive to the point of a rabid mania if he eats sugar; once in this state, he will often become obsessed with seeking any other source (and will also sometimes run around naked or in his underwear). He is voiced by Sean Marquette.
Wilt – A very friendly, very tall, red-colored friend with a stubby left arm and crooked left eyestalk (which he describes as "wonky"). However, in "Good Wilt Hunting", it is discovered that he was not always this way; he was injured in a fateful accident during a basketball game, leaving his arm crushed and his eye injured. Wilt exhibits consummate good sportsmanship, which he applies to every part of life he can. He's extremely courteous to a fault, often willing to help anyone, fix anything, and perform anything asked of him, (even if he has to go entirely out of his way to do so), and apologizes almost constantly (he is known for saying "Is that okay?", "Sorry!", "I'm sorry, is that okay?", and "I'm sorry, but that's not okay!"). He has a big heart, is cool and collected, and on very rare occasions can be moody or short-tempered. His name is a homage to NBA star Wilt Chamberlain. Wilt was shown to be created by Jordan Michaels, a basketball star (and a homage to Michael Jordan). His oversized basketball shoes always squeak against the floor/ground, no matter what surface he is walking on. He is voiced by Phil LaMarr.
Eduardo – A Spanish guardian friend. Despite his large size, overwhelming strength, and menacing demeanor, Eduardo is quite docile, timid, and compassionate. He has a toddler-like nature, crying at minor negative occurrences, and being scared of almost everything. However, he can be ferocious if angered or in the circumstance that danger befalls his friends. Eduardo has a fondness for potatoes and his cuddly toys. His creator, Nina Valerosa, is now a police officer. He is voiced by Tom Kenny.
Coco – A bird-airplane-palm tree friend who can only say (or write) her name at various speeds and different emphases. A talent unique to her is her ability to lay colorful, plastic eggs containing a plethora of objects from customized baseball cards to money, at will. Mac, Bloo, Eduardo, Frankie, Wilt, and others usually understand her when she speaks, and often translate for her (though Wilt once admits that he has no idea what she attempts to convey). Despite her helter-skelter appearance and quirky behavior, she can demonstrate a perceived intelligence, principle and kindness. She is also a skilled musician, which she can play a guitar-like instrument in "House of Bloo's" in the home's music room, the tuba in "My So- Called Wife", and the harp in "Goodbye to Bloo". No one knows who her creator is as she was found on an island by two scientists named Adam and Douglas. She is voiced by Candi Milo.
Frankie – Madame Foster's 22-year-old granddaughter, addressed as "Miss Frances" by Mr. Herriman. Frankie is the caregiver at Foster's and helps keep everything in order. In spite of Mr. Herriman's fussiness and fixation with rules and cleanliness, having to take care of everyone and everything in the house, and Bloo's mischief-making (all of which cause her tremendous stress), she is usually very friendly and easy-going. And though she may seem somewhat like Bloo's enemy, she is more accurately described as a big sister to the imaginary friends. She is voiced by Grey DeLisle.
Mr. Herriman – A British-accented, man-sized, bipedal rabbit friend imagined by Madame Foster. He wears a tuxedo coat, white gloves and a stovepipe hat, as well as a monocle over his left eye (though it is sometimes seen over his right eye). He is in charge of the house (the "President" of Foster's), is extremely strict about the house rules (or just politeness and order in general), and is often found punishing Bloo for his various misdemeanors. It was revealed in "Busted" that the reason Mr. Herriman is so hard on Bloo is because he feels that, given that he is allowed to stay at Foster's even though he still has an owner, he has already broken one of the main house rules. He is extremely fond of his creator Madame Foster, harboring great respect and loyalty to her, even at her most prominent levels of unabashed pep and energy. Mr. Herriman may be considered unruly Madame Foster's superego. On the other hand, Herriman has a love/hate relationship with Frankie, usually working with her to preserve order at Foster's, yet just as often scolding her for what he perceives (often inaccurately) as "laziness" and "immaturity" from her part (usually stemming from the fact that the amount of work she has to do is too much for her to get all of it done in certain time frames). However, at the end of the 90-minute special "Destination Imagination", Herriman admits that he was wrong and finally comes to respect and appreciate Frankie. Also he has a fear of dogs and will punish anyone who keeps dogs in the house it has been showed in the episode "Who Let the Dogs In?" He is voiced by Tom Kane.
Madame Foster – The founder of Foster's. Madame Foster is elderly but has child-like boundless energy, and enjoys life to the fullest. Her imaginary friend is Mr. Herriman who she imagined when she was a child and never gave up. Like Bloo, Madame Foster occasionally becomes hyperactive and mischievous. However, there are times she's shown to be the wisdom of the house. She is voiced by Candi Milo.
Berry - A sweet, short, red imaginary friend who is in love with Bloo, which causes her craziness for him to ensue, even to the point of trying to kill Mac so Bloo would no longer be with him and would be with her instead. Though she only appears in two episodes, she is still considered a minor antagonist. She first appears in "Berry Scary". She is nice at first, then she fell in love with Bloo in first sight, at which point she reveals a "sour", borderline psychotic side to her. She meets Mac, but wants him out of the picture so Bloo will be hers. Bloo doesn't return the feelings and can't even remember her name, but this doesn't stop Berry from believing that they are "meant to be". She returns in Season 5 in the episode "Affair Weather Friends", but does not reveal herself until the end. When her plot to kill Mac by running over him with a toy train fails, she winds up getting trapped in a giant rubber band ball, as she did in "Berry Scary". She is not seen or mentioned again after that. The combination of Bloo and her name makes the word, "Blooberry", a parody of the word "Blueberry". She is voiced by Grey Delisle.
Cheese – A simple, pale-yellow-colored friend who debuted in "Mac Daddy". Cheese was thought to be an imaginary friend accidentally created by Mac, but was actually created by Mac's neighbor Louise. He appears to be somewhat madcap and dim-witted, often saying incoherent or non-sequitur phrases, and breaking into sudden bouts of screaming when frightened or when he doesn't get his way. Cheese likes goldfish crackers, cereal, juice, chocolate milk (although he is lactose-intolerant), and so on. His name can be paired off with other characters' names to make puns-of-sorts ("Mac and Cheese"/ Macaroni and Cheese, "Bloo Cheese"/ blue cheese, "Cheese and Crackers," and "Cheese Louise"/ the expression "Geez Louise!"). In the series finale "Goodbye to Bloo", he becomes the newest resident at Foster's, much to the residents' surprise/horror. Cheese is always considered to be an annoyance, but is treated like a friend by Mac's friends in "Infernal Slumber". He is voiced by Candi Milo.
Duchess – A "high-maintenance" pedigree friend who is pompous, ugly, rude, and lazy up to the point she orders Frankie to open her eyelids for her first thing in the morning. She considers herself superior to all the other imaginary friends, is extremely negative towards everyone, and never says anything nice (despite this, she has helped someone in four episodes but only to help herself). Whenever Duchess turns on the spot, her entire body pivots like a sheet of paper being flipped, revealing that she is two-dimensional (however, in the pilot movie "House of Bloos", she was not two-dimensional). Her full name is "Her Royal Duchess Diamond Persnickity the First, Last, and Only". She is voiced by Grey DeLisle.
Goo – A hyper-imaginative, hyper-talkative 10-year-old girl who first appeared in the episode "Go Goo Go". Her parents allowed her to name herself when she was a baby resulting in the full name "Goo Goo Ga Ga". Goo enjoys playing games such as Checkers and Truth or Dare, but she does not know how to play and Mac is the only one who notices. In her first appearance she constantly created friends and finally stopped at the end. However, she has still created a few by mistake or to help on rare occasions. She is voiced by Grey DeLisle.
Terrence – Mac's 14-year-old brother. He enjoys keeping Mac, and coming up with various schemes to make Mac's life miserable. His stupidity always gets the better of him, making him easily outsmarted. He is voiced by Tara Strong.
Billy the Squid - A pink squid who appeared on "Cheese A Go-Go" went Frankie needed to pick up Wilt, Coco and Eduardo from the dentists and yelled "WHAT A GROUCH!!". He is based voiced by Tom Ruegger's son Cody Rueggers.
Ramone - A red or orange-colored friend with headphones on his ears, which are plugged into an iPod. He enjoys listening to music, and he also likes listening to heavy metal songs. He also speaks too loud due to the volume of the music he is listening too, and his speaking lines also frustrate everyone else at Foster's. His facial appearance is very similar to Dragonfly from Mucha Lucha.
Sassyfrass - A valley girl-like sounding friend. She often gossips about cute boys, and likes shopping. She is also a friend of Coco, as seen in the episode "Partying is Such Sweet Soiree". Also, she can cheer really loud, as seen in "Schlock Star".
Jackie Khones - A one-eyed, green-colored, stick-shaped friend. He likes to eat Chinese food, and he does not like being in large crowds. He also dreams of being a famous action-styled Hollywood actor. He even starred in his own episode called "Jackie Khones and the Case of the Overdue Library Crook". It seems as if he has a dislike towards Wilt. He also has a low-pitched voice, which is a parody of the voice that actor and singer Thurl Ravenscroft has.
Sunset Junction - A blue-colored bear friend. He is one of the most well liked friends at Foster's. He also has a talent for knitting clothes, which include sweaters, scarves, and hats, and is also often referred to as a giant fuzzy blanket or a real cuddlebug. Also, in the special "Good Wilt Hunting", his creator is revealed to be an old woman, who has the same talent as him.
George Mucus - A green-colored glop of goo-shaped friend with a broken arm. He often likes to post sci-fi websites on the Internet, with the handle "Greenmachine". He is also a parody of George Lucas.
Fluffer Nutter - A pink-colored squirrel friend who wears a pink bow on her head. She is a tomboy, and likes rock music and motorcycle riding. She also has a talent for playing the bass guitar, but however, she plays an electric guitar for the home's house band, "Pizza Party", as seen in "Schlock Star", and she also has a crush on Jackie Khones, as seen in "World Wide Wabbit", "The Little Peas", and "Read 'Em and Weep". She also dreams of hitting it big when she someday records her first album while having her music career.
Mr. Edmonton - A pipe smoking animal-like friend with ten legs and feet, and with a flower for a tail. He is also a talented dancer, and like Wilt, is really good at sports.
One Eye Cy - A green-colored cyclops friend with chicken legs. He is also the home's bouncer, likes sewing, and dreams of becoming a tailor. He also likes the color pink and cuddling with fuzzy little animals, and his favorite foods are corn dogs and green tea ice cream, but he will often make himself sick whenever he eats too much, and like Eduardo, is very compassionate.
Bloppy Pants - A gray-colored cat friend who is dressed in a coat and a scarf, along with mess-upped whiskers. He is very shy and anxious. He is often afraid, and is also very nervous. Also, he is afraid of his own shadow, and will sometimes cling to the safety of a scratching post. He also likes to eat kitty treats, and like Fluffer Nutter, is also a member of the home's house band, "Pizza Party", in which he is the vocalist of the band.
Pokey Toehair - A red, orange, and purple-colored furred friend. He also harbors a deep love and obsession for his very, thick coat of fur, and it sometimes causes him grief. Also, his coat often gets hot outside while during the summer, although his coat does not give everyone else allergies, and he also hangs out in the home's attic alone while during that type of season. Also, he likes smooth jazz music, and he also has a talent for playing the saxophone.
Mabel Licorice - A red and pink-colored bear-like dragon friend with freckles on her face. She also has a sarcastic pre-teen personality, and she also likes sweets. She is also very mischievous, and she can also jump rope really well, as seen in Big Fat Awesome House Party.
Iris - A many-eyed friend with one singular vision. Also, she has a talent for art, and she likes fashion and home decor. She is also talented for finding lost stuff, making her the home's resident detective.
The Tortoise In The Air - A tortoise that wears a helmet and goggles and has a mini-spaceship for a body, and can fly really fast. His name is a pun of "The Tortoise And The Hare".
Scissors - A scissors-shaped friend with girly eyes. He also likes the game of tag, and is Mr. Herriman's official document shredder. He is also the home's resident barber. Also, he likes to read mystery novels, and he also likes to listen to country music, while during his downtime. He is also a best friend to many of the hairier friends at Foster's. Also, he is named after the sentence, which is, "Never run with scissors".
Boris the Florist - A purple-colored friend with a tuff of black hair on the top of his head. He also likes floral arrangement, and he also likes to give Madame Foster a weekly gift of fresh flowers from his own, personal garden in the home's backyard. He is also known for maintaining all of the floral bouquets throughout the home.
Rodney Squiddlebeak - A blue-colored squid friend who wears a top hat on the top of his head, along with glasses. He often likes to have high tea with Mr. Herriman, and he also abides cucumber sandwiches that Frankie makes. Also, he can do various accents, such as an English gentleman or a street-smart wise guy from New Jersey. He is also talented for playing board games that involve spelling, and if he is about to loose, he will spray the opponent that he is playing with ink, and will also toss over the game board.
Charlie the Chicken Leg - A chicken leg-shaped friend. He does not like to be eaten, and he often hides with the other food-shaped friends while everyone is having dinner. He also mostly has nightmares recalling his time spent at a weight loss camp with his creator. He was best known for speaking, as seen in "Dinner is Swerved".
Creaky Pete - A grizzled old-bearded friend who always sits in a rocking chair that creaks, hence his name. He is also one of the most laid back of everyone else at Foster's. He also likes to tell stories, and he also speaks with a southern drawl. Also, he can carve stuff really well, and along with a knife.
Clumsy - A pink-colored, potato sack-wearing elephant friend. He is also accident-prone, and mostly trips, falls, and stumbles. He also likes to take showers, and he also has a talent for singing, while taking them. Also, he is a friend of Eduardo, and like him, likes potatoes.
Phineus B. Vurm - A worm-like human friend. He is also the home's resident bookworm, and he often has his eyes closed, but in two scenes and in one scene of "Phone Home" and "Setting a President", he had them open. He is also known for being armed with one of the highest IQ's at the home. His name may be a pun of the name "Phineas".
Don Lickles - A tongue-shaped friend with tongues for feet. He often gets tastes of what the home is all about. He also acts as the home's resident janitor, and he does not like it, but will not do it when Frankie does it, mopping them clean.
Ringo Rango - A weird-looking, blue-colored friend with a mop of hair, which matches his skin color. He is also a walking, talking pop-culture machine, and like Mr. Herriman, speaks with a British accent, which is really thicker than his. He also likes pop music, and of course, sweaters. Also, everyone else at the home cannot understand what he is saying, but that never stops him from talking a lot.
Piggy - A buck-toothed, three-eyed pig friend who likes everything about food. He also likes to read cookbooks, watch cooking shows on TV, and even paint pictures of fruits and vegetables, which he probably would eat. It may be hinted that he was brought to Foster's by Wilt, who found him at a grocery store, eating his way through the entire potato chip aisle, and he, like Charlie the Chicken Leg, was seen in "Dinner is Swerved". He is also known for his enormous appetite.
Dusty - A red and black-colored fur ball friend who has legs. He is also a carefree leader of a group of other fur ball friends at the home. Also, he often likes to read books or watch old black and white movies. He also has a great sense of humor, and he also likes to play pranks on everyone else at Foster's, along with his gang of fur ball friends, and he is also known for saying, "They don't make 'em like they used to!" at some points.
Myopic Patootie - A yellow-colored animal-like friend with an eye on the back of his bottom. Everyone else at the home often makes fun of him, but they never do it often.
Yogi Boo Boo
Burple Bear - A width-sized light purple-colored teddy bear-like giant friend, who often smiles a lot, but occasionally frowns in several episodes that he appears in. He is also one of the residents at the home to never speak. Also, his name may be a pun of the word "Purple Bear".
Vic Trolla - A trumpet-like record player friend. Also, he is one of the residents at the home to never speak, like Burple Bear, and also, his name may be a pun on the word victrola.
Jethro Precious - A barrel along with flowers-wearing leafless, tree-shaped friend. Also, like Boris the Florist, he has a tuff of black hair on the top of his head.
Galoot Palooka - A dark purple-colored caveman friend. Like Boris the Florist and Jethro Precious, he has a tuff of black hair on the top of his head.
Suckallupagus - A purple and pink-colored vacuum like friend, and like Mr. Edmonton, he looks like an animal. He is also known for appearing in the very beginning of the episode "The Trouble with Scribbles".
Nose Allison - A blue-colored, nose-faced kangaroo friend. Like all other kangaroos, she has a joey that sits in her pouch.
Spritz Coleman - A gray-colored raincloud-shaped friend. Also, like Burple Bear and Vic Trolla, he is one of the residents at the home to never speak.
Clambake - A white-colored bone-like friend who wears a bow tie. Like Phineus B. Vurm, he is very smart, and they both seem to be best friends, as seen in "Setting a President".
Pinecone Cola - A dark red-colored dragon-like lizard friend. When he speaks, he sounds like Jake Spidermonkey from My Gym Partner's a Monkey. Also, in "Good Wilt Hunting", his creator is revealed to be a teenage girl who has the same hair color as him, who seems to have a crush on him.
Bellybob Norton - A dark green-colored, Sesame Street character-like friend. Also, that his name implies, his bellybutton is always shown, and he also wears a shirt that is too big for him, which he never complains about. He is also one of the residents to never speak, which also include Burple Bear, Vic Trolla, and Spritz Coleman, and also, his name may be a pun of the Rockafire Explosion character, "Billy Bob Broccoli".
Dyno - A purple-colored, sweater wearing dinosaur friend. Also, like Phineus B. Vurm and Clambake, he is very smart, and he, like, Burple Bear, Vic Trolla, Spritz Coleman, and Bellybob Norton, is one of the residents at the home to never speak.
Chester n' Nester - A pair of friends that consists of a beige-colored raven-like human friend (Chester) and a orange-colored fur ball friend with the style of legs and feet that that the characters Lazlo, Raj, and Clam have from Camp Lazlo, and the arms and hands that the Disney character Mickey Mouse has, and is also nested inside his cowboy hat (Nester). Like Creaky Pete, they both speak with southern drawls. Also, whenever Chester speaks a long sentence, Nester will often pop out to repeat the middle, end, or both of the sentence, which is how the Mirmo! characters the Warumo Gang repeat. They are also a parody of the Dr. Seuss characters, the Cat in the Hat, and his assistants, the Little Cats.
Jimmy Shoes - Another fur ball friend with alienantennas and legs, and the shoes that he is wearing on his feet are somewhat similar to the shoes that Wilt wears on his feet. Also, he is also known for appearing in "Bad Dare Day".
Unknown Friend - A weird-looking friend with a paper mask for a head and with a rubber chicken body for a body. Also, like Phineus B. Vurm and Dyno, he wears glasses, and also, like Burple Bear, Vic Trolla, Spritz Coleman, Bellybob Norton, and Dyno, he is one of the residents at the home to never speak, until "Goodbye to Bloo".
Chief Hoseynose - Another elephant friend who is dressed up like a firefighter. He was also known for appearing in one of the videos that the friends uploaded on the ViewTube website in the episode "Bloo Tube", in which he was watching TV while eating cookies and milk, and which he was interrupted by Frankie and Mabel Licorice.
Socket Tubey - A television-like creature friend who has TV antennas for arms and hands, a vehicle's tire for movement, and a sock puppet for a head and a face. Also, like Scissors, he also has girly eyes. Also, when every time when he is shown, his television screen body often features a couple dancing together or about ready to kiss.
Pisgetti - Another one-eyed friend who looks very similar to Jackie Khones, but instead has a fat body with his mouth located on the very top of it. Also, like Jimmy Shoes, he was also known for appearing in "Bad Dare Day".
Fridgy - A refrigerator friend who always looks worried. He was also known for making a small cameo in "Partying is Such Sweet Soiree", and also being the only character in the end credits of that same episode.
Myron Giant - Another width-sized robot friend. He was also known for participating in the "Dare Cup" in which his dare features that he tries to eat pickles, making him refuse, and making Bloo win his "Dare Match" with him, as seen in "Bad Dare Day". Also, his name may be a pun of the movie title, The Iron Giant.
Stoolie Dan - A blue-colored, polka-dotted turtle-like stool friend, hence his name and also, his name may also be a reference to the band Steely Dan. He was also known for appearing in "Bloo Done It", in which that features him cheering with everyone else for the news. Also, he is one of the many lesser-known residents at the home to never speak.
Madame Mustachio - Another weird-looking green-colored friend. She was also known for appearing as one of the residents in the group photo in "The Big Picture" . Also, she may look very similar to Jackie Khones and Pisgetti, but instead has a green mustache, hence her name. She is also one of the residents at the home to never speak, and if she did spoke, she might have a voice sounding very similar to Ms. Chameleon, another character from My Gym Partner's a Monkey.
Jambalaya - A purple-colored octopus-like creature friend, and (like Medusa) having snakes in place of hair. Also, she was best known speaking in "World Wide Wabbit", and whenever she speaks, she might speak like Homsar from Homestar Runner.
Moptop - An imaginary friend with wheels, and pink hair. He has been called "Wheelie" in the episode "Beat With A Schtick". His only line is "Aah!! Make him stop, MAKE HIM STOP!"
Witch Itch - A bug type imaginary friend with a witch's hat with an eye attached to it.
Cowboy Cow - A cow-like imaginary friend with a cowboy hat. He is mostly shown at the end of the table at breakfast, lunch, or dinner. Like Burple Bear, Vic Trolla, Spritz Coleman, Belly Bob Norton, and Dyno, he never spoke.
F. P. Doodle - Stick figure imaginary friend.
Pirate Pig - Pig imaginary friend dressed as a pirate.
Jim Centaurino - Green centaur imaginary friend.
Crayon - Crayon imaginary friend.
Sockagewea - Purple sock imaginary friend who is seen helping with laundry in House Of Bloo's.
Dennis - A yellow sponge-like imaginary friend. Like Burple Bear, Vic Trolla, Spritz Coleman, Belly Bob Norton, Dyno, and Cowboy Cow, he is one of the residents at home to never speak.
Two-Head Fred - A yellow twin 2 guys holding a wand imaginary friend. They make several cameo appearances.