The movie Abed was filming with Chang is from the 'Police Justice' script he showed Buzz Hickey in the episode Bondage and Beta Male Sexuality (2014). Hickey offered to help make the dialogue more "realistic". Abed comments that "real life former cops aren't great with dialogue," after Chang says one of Hickey's phrases ("I'm gonna punch you in the heart").
The Glipglop featured in the movie appears earlier in Dan Harmon's animated series Rick and Morty (2013).
In Ladders (2015), one of the police officers is in a carrot costume because they "ran out" of police uniforms. Magnitude can be seen wearing the same carrot costume in the space bar scene, presumably because they ran out of costumes again.
Frankie playing the steel drums in the space bar scene is a reference to the previous episode, Advanced Safety Features (2015). Jeff told Frankie that Troy had been a group favorite because he played the steel drums.
The space garbage that Britta, Jeff and Annie fall into is made up of the Frisbees that collapsed the roof in the first episode of season 6, Ladders (2015).