For the theatrical run, a small cough could be heard during the opening Sony logo. It was taken out of the DVD and Bluray releases to prevent viewers from thinking someone was in their home.
Kurt Russell mentioned that his son Wyatt Russell turned down a role for The Hunger Games sequels to star in this movie.
Maya Angelou died two weeks before the film's release, and they had no time to swap out the reference. They decided it was okay, though, as it's not disrespectful.
The film originally ended with Jenko and Schmidt saying they never wanted to do this again, but test audiences didn't respond well so they created the multiple variations -- medical school, a semester at sea, etc -- just a month before the film opened.
They were all floored by Jillian Bell's banter with Jonah Hill in the morning scene. The filmmakers note that it was the first time they ever saw Hill on his heels. "It's like she thinks about what I'm gonna say before I say it and says it better and funnier than I was."
Dustin Nguyen: of the original 21 Jump Street (1987), as the Vietnamese Jesus in a deleted scene: Jenko's dream sequence while he's high on WHYPHY.