* AttentionDeficitCreatorDisorder: Mike Portnoy, with side-projects such as LiquidTensionExperiment, OSI, and TransAtlantic, and even moreso after he left the band. Also Jordan Rudess in 2013, who is working on no less than four musical projects [[note]]''Dream Theater'', ''Explorations for Keyboard and Orchestra'', ''All That Is Now'', and ''Levin Minneman Rudess'', as well as guest work for Eyal Amir and Ayreon[[/note]] and continuing to develop and promote various apps [[note]]Ear Wizard, the Explores app, Jam Bandit[[/note]] and technologies[[note]]Roli Seaboard, Ableton Push, Touch Keys[[/note]].
* AudienceParticipationSong: James will often get the crowd into singing along with the band, but that's nothing compared to Portnoy's Audience Participation ''Drum Solos'', complete with call-and-response "Shave and a Haircut".
* CreativeDifferences: One of the reasons Kevin Moore left the band after ''Awake'' (the others being his increasing alienation from bandmates and ReclusiveArtist behaviour), and the main reason Dominici left after ''When Dream and Day Unite''. (The band did not have major issues with Dominici but felt his vocals did not fit their style particularly well - Portnoy called the result "like having Music/BillyJoel singing in Music/{{Queensryche}} -, and he amicably left the band after the album was recorded.)
* CreatorBreakdown:
** Many songs came from Mike Portnoy's problems while writing the lyrics.
*** The "[[http://en.wikipedia.org/wiki/Twelve-step_Suite Twelve-step Suite]]" is a series of five songs in twelve parts written by him, which chronicles his experience with [[TheAlcoholic alcoholism]]; also known as the "Alcoholics Anonymous suite". "The Mirror" is also about alcohol, written well before he became sober.
*** "The Best of Times", from ''Black Clouds & Silver Linings'' and "A Change of Seasons", from ''A Change Of Seasons'' were written about [[GriefSong his late father and mother]], respectively.
*** "Never Enough", from ''Octavarium'', is a TakeThat towards DT's UnpleasableFanbase. [[invoked]]
*** "Honor Thy Father", from ''Train of Thought'', is a TakeThat towards Portnoy's stepfather.
*** The unreleased "Raise the Knife" is about Kevin Moore's departure from the band.
** Kevin Moore also contributed "6:00" (about getting sick to work with the band) and "Space-Dye Vest", the latter of which is just depressive in general, both from ''Awake''.
** John Petrucci wrote "Take Away My Pain", from ''Falling into Infinity'', [[GriefSong after his late father]].
*** Also, "A Nightmare to Remember", from ''Black Clouds & Silver Linings'', is about a car accident where he was involved as a child.
*** "Wither", also from ''BC&SL'', is about writer's block.
** James [=LaBrie=] also has his share:
*** "Disappear", from ''Six Degrees of Inner Turbulence'', was written after he observed a young couple in a mall and wondering about what they would do when one of them dies.
*** "Vacant", from ''Train of Thought'' was written about the helplessness he and his wife felt after their daughter suffered a severe seizure.
* 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.
* OneHitWonder: Only "Pull Me Under" charted high enough to be considered a real hit. The band [[LampshadeHanging lampshaded]] this with the title of their GreatestHitsAlbum: ''Greatest Hit (...And 21 Other Pretty Cool Songs)''.
* 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.