"Go Goo Go" is the seventh episode in season 3 of Foster's Home for Imaginary Friends. The episode aired on November 11, 2005. This was Goo's first appearance on the show.
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 all of Goo's continuous visits. After Mac yelled at Goo when he told that he won't come to Foster's anymore, he decides to leave, never to return. Everyone at Foster's no longer cared for him. Not even Frankie, his now former girlfriend. The only one who cares about him was Goo.
- Running Gags:
- Goo calling Bloo “Chester”.
- Mac trying to talk to Goo, but she gets totally distracted.
- Bloo running and laughing wildly and crazily after Mac and Goo.
- Goo creating an imaginary friend or more to compare with the originals, such as Bloo, Wilt, Coco, and Eduardo.
- Mr. Herriman and Frankie getting ticked off at Mac for not following the rule about keeping Goo away from Foster’s.
- Everyone thinking Goo is Mac's girlfriend.
- Mac confronting Goo for getting him in trouble.
- Despite appearing, Madame Foster has no dialogue.
- When Mac tells Bloo Goo's gone, he does the same dance as in House of Bloos after Bloo drops the vase on Terrence.
- Frankie, Bloo, Coco, Eduardo, Wilt, Madame Foster, and Mr. Herriman turn against Mac after he was told he won't come to Foster's anymore.
First episode to feature Goo.