* CrossDressingVoices: Terrence is voiced by Creator/TaraStrong.
** Cheese is voiced by Creator/CandiMilo, who also voices Madame Foster and Coco. And [[WesternAnimation/ChalkZone that other blue dude.]]
** In the Japanese-language dub of the show, Mac is voiced by Makoto Tsumura, who currently voices Anime/AstroBoy.
* DawsonCasting: Eight-year-old Mac is voiced Sean Marquette, who was about fifteen or sixteen when the show began. He was not replaced after he had gone through puberty. Instead, he had his voice digitally pitched up. It is obvious if one compares episodes from Season 1 to episodes afterward.
* FakeBrit: Kansas native Tom Kane as Mr Herriman. He mostly pulls it off, but certain pronunciations may give the game away.
* HeyItsThatGuy: A guy looking suspiciously like [[Franchise/TheHitchhikersGuideToTheGalaxy Arthur Dent]] is on the side of the road in the episode where Bloo hijacks a bus.
** Mac walks into a bowling alley and passes by [[TheBigLebowski The Dude, Donny, and Walter]].
* HeyItsThatVoice: Where do we start?
** Bloo is the second version of [[Disney/{{Bambi}} Friend Owl]].
*** He's also [[KingdomHeartsChainOfMemories the ruler of Castle Oblivion]]. How fitting...
*** Less fittingly, he's also [[VideoGame/FirstEncounterAssaultRecon Lieutenant Steve Chen]].
*** In Japan, his voice actor is Creator/NoriakiSugiyama ([[{{Anime/Naruto}} Sasuke]])
** Eduardo is SpongebobSquarepants and [[RockosModernLife Heffer]].
*** Who is also now [[Disney/WinnieThePooh Rabbit]], as of the 2011 movie.
** Coco, Madame Foster, and Cheese are [[MuchaLucha The Flea]], [[WesternAnimation/MyLifeAsATeenageRobot Nora Wakeman]], and [[ChalkZone Snap]], respectively.
** Frankie and Goo are [[WesternAnimation/TheFairlyOddparents Vicky]], [[WowWowWubbzy Wubbzy]], [[WesternAnimation/TheGrimAdventuresOfBillyAndMandy Mandy]], [[WesternAnimation/AvatarTheLastAirbender Azula]], and [[WesternAnimation/DannyPhantom Sam]].
*** In Sweden, Frankie is also Azula.
** Wilt is [[WesternAnimation/{{Futurama}} Hermes Conrad]], [[JusticeLeague Green Lantern]] and [[SamuraiJack Samurai Jack]].
** Mr. Herriman is [[ThePowerpuffGirls Professor Utonium]] and [[StarWarsTheCloneWars Yoda]].
** [[PlayingAgainstType Believe it or not]], Terrence is {{Tara Strong}}.
** Mac is [[VideoGame/KingdomHeartsII Pence]].
** Ivan and Uncle Pockets, two one-off imaginary friends, are [[Disney/LiloAndStitch Pleakley and Gantu]], respectively.
* KeepCirculatingTheTapes: Seasons 1 and 2 have been released on DVD, though both have been out of print for years (with sets of season 2 going for as much as $70.00! ). Luckily the entire series is available on iTunes and the Playstation Network.
* NamesTheSame: Jackie Khones is named after Executive Producer Khaki Jones.
* [[TalkingToHimself Talking To Herself]]: [[GreyDeLisle Frankie]] with either Goo or Duchess.
* WhatCouldHaveBeen: In the earliest sketches of the show, Mac was blonde and had shorter hair.
* WriteWhoYouKnow: Mac is based on creator Craig [=McCracken=] as a child. Frankie, meanwhile, is based on his wife, Creator/LaurenFaust, as she is now.