Nemesis (full name: Nemesister) is a supervillain and the main antagonist in the episode "Challenge of the Super Friends" and was created in a situation involving brother-and-sister rivalry of her owner. Bloo became her sidekick purely out of anger, and an urge for revenge when Mac became Imaginary Man's sidekick and got hair gel all over his face, leaving him alone while he weeped until Nemisis came. She made him a costume (a black unicorn) and named him Uniscorn. He and Nemisis became the main enemies in this episode and fought against Mac and Imaginary Man. In the end, Imaginary Man and Nemisis get adopted and Mac and Bloo are reunited. She is voiced by Grey DeLisle, the same person who voices Frankie Foster and Goo.
Overall, Nemesister has a mixed personality. She is mean, evil, and sadistic but also pink-loving and obsessed with all things cute and girly. Her main goal is to conquer the world through stereotypically feminine objects (flowers, perfume, stuffed animals, etc) and let only girls have rights. She seems to be determined, yet cocky when it comes to battling, but more calm when she is at her lair. She is also easily angered, but also prone to whining when she's sad, as seen when Uniscorn (Bloo) betrayed her in the laundry room. As she began by yelling at him, only to sound sincerely hurt by his betrayal moments later.
Nemesis wears a short, black, strapless mini dress with white frills at the bottom and a pink chain belt with a giant heart on it (possibly a purse). Her hair is very poofy and is a slightly darker pink then her skin and it has a small white bow in it, her eyes are light blue with no pupils, she also wears thigh high black boots and black gloves that go up to her shoulders.
Nemesis has five parts of her body shaped like hearts:
- Her hair.
- Her head.
- Her upper body.
- her belt on her dress.
- Her boots.
Nemesis has a few notable abilities as seen in the episode, these include:
- Shooting a shower of flowers at her opponent.
- Creating items associated with younger girls.
- Firing a rideble rainbow or a deadly rainbow blast.
Nemesis is very powerful, to the point of almost unstoppable, unless her hair gets messed up, then she loses her powers.
- It could be possible she could have secretly loved Bloo due to her saying they had "something special" in the end.
- The name "Nemesis" is most likely used as an irony joke, seeing as she is portrayed as a sweet little girl in some moments of the episode.
- Nemesis' appearance could be an inspiration to the Powerpuff Girls, additionally, she is themed after hearts, which is also what the Powerpuff Girls are themed after, and the rainbows she fires are similar to the rainbows lefts behind whenever the Powerpuff Girls fly.
- Her golden trading card statistics in the Foster's Home for Imaginary Friend's Leapster game include:
- Is a superheroine!
- Her arch-nemesis is Imaginary Man.
- Likes going to the hair salon.
- Changes Bloo into UniScorn.