* ActorExistenceLimbo: Creator/MichaelJeter, who played Mr. Noodle's brother, suffered a fatal seizure in 2003, while the show was still in production. The character would not return to the segments until 2017, when ''Elmo's World'' itself was rebooted. For the new segments, there are ''two'' brothers of Mr. Noodle (played by Daniel Koren and Creator/DaveedDiggs), alongside Creator/BillIrwin reprising his role as the original Mr. Noodle.
* RealitySubtext: [[WordOfGod According to Kevin Clash]], Mr. Noodle's brother Mr. Noodle was created because Bill Irwin was unavailable due to being busy with ''Film/HowTheGrinchStoleChristmas''.