Most of their music videos also include a host of friends from bands on Pete's record label Decaydance.
Seth Green and Michelle Trachtenberg (both from Buffy the Vampire Slayer) show up briefly at the funeral scene in "Arm's Race", and the chick who plays Cerie on 30 Rock is the mean girl in "Dance, Dance"
Brendon Urie and Spencer from Panic! at the Disco make an appearance in the video for "What a Catch, Donnie".
The "A Little Less Sixteen Candles" video has William Beckett and Mike Carden from The Academy Is..., Travie McCoy from Gym Class Heroes, and Brendon Urie and Spencer Smith from Panic! at the Disco all as various vampires from different clans.
Cassadee Pope, then of Hey Monday and later on of The Voice, cameos in the "America's Suitehearts" video.
The music video for "My Songs Know What You Did In The Dark (Light Em Up) consists entirely of 2Chainz and two other women setting fire to Fall Out Boy's discography and memorabilia.
Big Sean shows up in the video for "Alone Together", as set up for his (assumed) appearance in The Mighty Fall.
William Beckett sings in "Sophomore Slump or Comeback of the Year".
The other screaming voice on "I Slept With Someone in Fall Out Boy and All I Got Was This Stupid Song Written About Me" is Chad Gilbert of New Found Glory.
In "7 Minutes in Heaven (Atavan Halen)" and "20 Dollar Nosebleed", Brendon Urie lends his vocals. However, it may be hard to pinpoint his parts as he and Patrick have similar voices and singing styles.
In "What a Catch, Donnie", a few guest stars lend their voices to sing a few of their greatest hits.
You know the second singer in "Save Rock and Roll"'s title track? Its only Elton Fucking John!
Courtney Love is featured on "Rat a Tat", Big Sean on "The Mighty Fall", and Foxes on "Just One Yesterday".
One of Us: One of their first tours in support of From Under The Cork Tree was the Nintendo Fusion tour, they did two alternate reality games for Folie a Deux and their Greatest Hits album, did an entire photoshoot with lightsabers, and on one of their blink-182 reunion support dates, they did a set dedicated to LOST.
In terms of One Of Usness...Andy, Pete, Patrick, Joe. Arguably.
Andy is a big comic book fan, Patrick has a preference for oldschool video games (when he gets a chance to play), and Joe used to go into long, elaborate blog posts about Star Wars back in the Take This To Your Grave days.