The band go to a high school prom, simultaneously playing and attending as geekier versions of themselves.
It's also based on the 80s, featuring the geeks triumphing over the cool people.
Notably, about a minute and a half in, lead guitaist Joe Tromhan does a move now called Trohmania, jumping up and spinning with his guitar.
Patrick Stump's dancing is a particular highlight.
At the very end all members have found love, and Pete Wentz does the Thriller dance!
The video is a little longer than the song, thanks to an intro bit, and a few seconds of improvised dialogue.