There have been several WMGs regarding Deandra's secret for leaving Atchison High. Most of which that were included was her, pooping all over the place in the middle of a cheer routine and they were spot on!
Throw It In: Since most of the cast is experienced with improv, a lot of the lines in the series aren't in the script. In the Behind the Scenes video, the creators have stated that some of the funniest lines were made up on the spot.
Special mention goes to Bridget Tice's dialogue. Pretty much all of her lines were made up by the actress.
The famous scene from season 1 that is being dubbed the "Trisha monologue" is improvised as well. And what we heard was only a portion of the full speech Garrett (Trisha's VA) made up.
MPGIS wasn't originally supposed to be a serialized show with a bunch of episodes. Episode One was just called "Bathroom Hierarchy".
Mikayla was originally not a Van Buren.
Jenna Darabond and Jenna Dapananian would've showed up in Episode 5.
Deandra was originally going to be hailed as some sort of prophet, as in to save Overland Park, and humanity.
Trisha was supposed to be voiced by a girl when they were creating their very first video but her actress didn't show up. So they settled for one of the guys to do her voice. Of course, due to the current state of things, nobody would want it in any other way.