* ActingForTwo:
** Jamie Kennedy as Kyle and Fankylechum.
** Candi Milo as Nancy, Francine, and Cher Leader.
** Jeff Bennett does the voices of many recurring characters, including Mr. Mufflin, Duke, Boog, and Agent Johnson, the latter two who argue with each other in "A Bopwork Orange". He also voices Man-Arctica and his ArchEnemy, the Global Warmer, who have a lot of scenes together when brawling.
* AllStarCast: The show as a lot of famous celebrities (Josh Duhamel, Creator/JamieKennedy, etc.) voicing a good number of characters, alongside voice actors like Creator/JeffBennett and Candi Milo.
* ApprovalOfGod: The show's creator has liked fanart depicting Kyle as trans and has stated he would implement it in a hypothetical continuation/reboot.
* BillingDisplacement:
** Yo is credited as one of the main characters despite not being as prominent as Kyle and most of the time, she doesn't even talk in the episodes, making her more of a recurring character.
** The end credits for all episodes list all voices after Fanboy and Chum Chum alphabetically, placing Kyle's voice near the bottom even in episodes where he has a starring role.
* CowboyBebopAtHisComputer: The descriptions and script of "Little Glop of Horrors" say the cafeteria is serving grey glop; in the actual episode, the glop is ''red.''
* CrossDressingVoices: Nika Futterman as Chum Chum.
* TheDanza: Lucky Charlie in "Lucky Chums" is voiced by Creator/CharlieDay.
* FakeBrit:
** American Jamie Kennedy as Kyle.
** When Chum Chum believes that he is Kyle in "Lord of the Rings", he begins speaking with a British accent.
* FakeNationality: Creator/JeffBennett fakes a German accent with Sigmund, and an Austrian one with the Dollarnator.
* IronyAsSheIsCast: Kyle has never had a song to himself in the series; his voice actor, Jamie Kennedy, is a professional singer.
* KeepCirculatingTheTapes: Only two [=DVDs=] were released, though both seasons are available on Creator/ParamountPlus and Creator/AppleTVPlus.
* TheOtherDarrin:
** Creator/NancyCartwright voices Chum Chum in the original ''WesternAnimation/RandomCartoons'' pilot as opposed to Creator/NikaFutterman in the main series.
** Lenny was originally voiced by Creator/JeffBennett in the pilot before Wyatt Cenac voiced the character for the series proper.
** Francine’s one line in “Pick a Nose” was done by Annie Mumolo instead of her usual voice actress Creator/CandiMilo.
* PlayingAgainstType: Josh Duhamel, who usually plays badasses in live action, does the voice for Oz, a comic book collector who still lives with his mom.
* ReleaseDateChange:
** The episodes "Risky Business", "Kids in the Hall", "Crib Notes" and "[=HypnotOZed=]" were going to air on August 6, 2011, but were delayed at the last minute to August 27.
** "There Will Be Shrieks" was going to air on October 22, but was pushed forward one day later to make room for a ''WesternAnimation/SpongeBobSquarePants'' rerun.
* ScrewedByTheNetwork: One of the biggest examples of this on Creator/{{Nickelodeon}}. After being AdoredByTheNetwork for 2 years, the show was moved to a 7:00am timeslot and had several episodes delayed for a solid ''year and a half''. In fact, it's final episode, "Brain Freeze" (which was initially a DVD exclusive), didn't air until ''2014, nearly'' '''''three years''''' ''after the [=DVD=] release'', after a rerun of ''Series/PowerRangersSuperMegaforce''. Reruns were also practically nonexistent, as the show would air only on Sundays at 7:00 am from mid-2013 to early 2015, when it was banished permanently.
** The treatment it got on Creator/{{Nicktoons}} wasn't great, either. The show usually aired between 4:30am and 6:00am after it ended until March of 2016, when it disappeared completely.
* ThrowItIn: Kyle's line "The Great Griffon!!" in "Wizboy" when he spots the great griffon flying through the air was not in the original script. It was ad-libbed by Jamie Kennedy last minute.
* WordOfGod: According to Eric Robles, Chum Chum is two years younger than Fanboy, but is in the same class as him due to sneaking him in without anyone noticing.
* WhatCouldHaveBeen: Tons.
** The PilotEpisode "Wizboy" was to have a scene in the hallway right before the lunch scene; also, some dialogues were longer.
** For "Pick a Nose", the boys' preparation scene was longer, such as Fanboy painting his head. Also, the boys originally got dirty by crawling in a dumpster, while in the episode, they repeatedly sniff a dirty Chuggy.
** Two scenes in "Trading Day", one involving Yo sneaking away with Chum Chum in her mouth and Kyle with his own Mechatech. These scenes were restored for the novelization.
** The episode "I, Fanbot" had an alternate opening where the boys watch Kyle make a potion with his Lil' Warlock Kit, and Fanboy is caught drinking from it before burping up a smoke skull (Which explains why Kyle is sitting between the boys in the first shot). This was removed in the final version as it was deemed too harsh and unsettling, and skipped to the scene where Mr. Mufflin announces the test, and Fanboy is caught making a weird face instead.
*** Originally, Oz removed Fanboy's brain first; in the episode, he takes out the robot's brain first. Also, the robot didn't speak originally, he was given a voice near the end of production.
** There was an extra scene involving the three boys giving out a note in the hallway in the script and storyboard for "Excuse Me".
** "Present Not Accounted For" originally had Dollarnator giving Chum Chum a joke-of-the-day calender; in the final episode, [[TheVoiceless he had no lines]], and [[TheUnreveal his gift remained unknown]]. Also, Kyle's dramatic monologue originally started right when he was introduced, and was a little different.
** The HalloweenEpisode "There Will Be Shrieks" was originally going to end with the boys not getting their taste back, and Chum Chum's grapes from earlier falling out of the sky into his bowl.
*** Kyle's first scene in said episode is much different in the storyboard than the episode. In the storyboard, he is sitting at a desk reading from a book; in the episode, he grabs a book off the bookshelf to read it.
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