|Go Goo Go|
|Episode name pun on: Go Dog Go|
|Airdate:||November 11, 2005|
"Foster's Goes to Europe"
"Crime After Crime"
When Bloo leaves a snowboard up in a tree, Mac climbs up to get it back down. He tries to reach for it but he can't hold the tree much longer and ends up falling down, but his backpack holds the branch to safe his life, however the strap of his backpack rips off and Mac falls back down in a mud puddle. When Mac falls on a girl named Goo, she begins visiting Mac every day at Foster's. With her hyperactive imagination, she creates a new friend one after another, which causes a big problem for the other imaginary friends in the house. After she creates so many imaginary friends that it crowds the whole house, the others have to sleep in the Foster's bus and feel that Mac is responsible for Goo's continuous visits.
- First episode to feature Goo.