* HeyItsThatVoice:
** "Repentance", from ''Systematic Chaos'', has [[{{Yes}} Jon Anderson]], [[PorcupineTree Steven Wilson]], ChrisJericho, [[{{Slipknot}} Corey Taylor]], [[Music/{{Megadeth}} Dave Ellefson]], Steve Vai, Joe Satriani, and then some.
** Doug Pinnick sings a part in "Lines in the Sand", from ''Falling into Infinity''.
** The hypnotherapist in ''Metropolis Pt. 2'' is played by Music/{{Rush}}'s RecordProducer Terry Brown, while Edward is voiced by Music/{{Tool}} producer and original engineer David Bottrill.
* MemeAcknowledgment:
** In a magazine interview, John Petrucci said he thought the Psycho Exercises GagDub videos were hilarious. On the extra material of the ''Chaos in Motion'' tour DVD, he [[http://www.youtube.com/watch?v=LF8RNQmhbCE imitated them]].
** There was also a show in Perth, Australia that had to be moved to a new venue, among other complications, so a fan created a parody of The Fall. Portnoy saw it, thought it was hilarious and proceeded to have it played before the first song at the show.
* WhatCouldHaveBeen:
** ''Falling into Infinity'' was supposed to be a double album, but [[ExecutiveMeddling the record label]] wanted it to be [[LighterAndSofter less proggy and more radio-friendly]]. Also, a shorter version of the song "Metropolis Part 2", before it was turned into an album, was going to appear in the second disc.
** Petrucci felt that ''Metropolis Pt. 2'' needed a "heavier and larger" mix and called in Kevin Shirley was to remix it, but due to time constraints, Bottrill's original mixes of "Regression", "The Dance of Eternity", "One Last Time" and "Finally Free" were left on the album.