The Nostalgia Critic: In "Battle of the Commercials", while reviewing the commercial for Spider-Man (Atari 2600), among other things, the Critic misinterprets the Green Goblin's "You're running out of fluid!" line as "You're running out of Bloo wigs!", and shows a picture of Bloo wearing a wig.
SuperMarioLogan: In "Jeffy's Foster Home!", when Mario asks Officer Brooklyn T. Guy what would happen if he beat Jeffy in front of him, and Brooklyn tells him that he'd have to take Jeffy to a foster home. Brooklyn then brings up Foster's Home For Imaginary Friends, saying it was a good show, and also asking what the name of the blue imaginary friend was, before realizing his name was Bloo.
The Buzz on Maggie: A replica of the house appears as one of the dishes at a termite restaurant.
Craig of the Creek: Eduardo makes cameos in the episodes "Sparkle Cadet" (as a home-made mask) and "Cousin of the Creek" (as a stuffed animal).
The Grim Adventures of Billy & Mandy: One episode has Billy watching an obvious parody called "Fister's House for Crazy, Weirdo, Made-Up People". It's just the residents and a vaguely Mac-looking character talking over each other until it cuts to the outside of the house, which randomly explodes.
Kid Cosmic: One of the child actors shown in "Kid Cosmic and the Secret of the Fourteenth Stone" looks remarkably like Mac.
MAD: Bloo appears among the Cartoon Network characters in "Once Upon a Toon".
The Powerpuff Girls: Mac, Bloo, and Frankie make cameos in "The Powerpuff Girls Rule!!!"
Robot Chicken: A sketch from "Joel Hurwitz" has a little girl visit Foster's. After rejecting Bloo, Wilt, Eduardo, and Coco, she chooses to adopt Tyler Durden from Fight Club as her new imaginary friend.
" one of Bot's "facts" about themself to Cabby is that their full name is Botregard Q. Kazoo, in reference to Bloo's full name.