As Dan Harmon explained in a behind-the-scenes commentary for the season 3 episode, the writers only realized as they were writing the script that the characters had already said “Beetlejuice” two times before, so they decided to roll with it. But although the joke wasn’t quite as planned out as it seemed, it still demonstrates how good the “Community” writers were at remembering what they’ve done. The writers were always willing to take the show’s history and play around with it in fresh, subtle ways, regardless of whether casual viewers could reliably pick up on it or not. This was a habit that continued all the way into season 6, which memorably featured a meta-joke around Frankie (Paget Brewster) that likely confused the hell out of a major section of the audience.
The joke was playing with the fact that, before she joined the show as a main cast member, Brewster had a minor, one-off role as an IT lady for the school in season 5. In season 6, Frankie remarks, “I’m trying to find the IT lady. My emails to her get bounced back to me in Aramaic, and when I call, I hear an undulating high-pitched whistle that makes my nose bleed.” It’s a joke that only makes sense if you remember Brewster’s unremarkable 40-second scene in the previous season. If you didn’t, it’s a joke that’ll seem like randomness for the sake of it.
With the “Community” movie in the works right now, there’s no telling what sort of weird, barely-noticeable jokes the writers will have in store. We still know nothing about what the movie’s about, but we can at least trust that the writers’ attention to detail isn’t going anywhere.