I would change the name of the hostages from any vahz or BP mission to first names of characters of zombie games (frank, jill, leon, etc).
The word cowabunga would be somewhere in the sewer or abandoned sewer network.
Hellion AV Tinder would say swipe left/right. (thats low hanging fruit, i know)
There would be a cutscene that made fun of players using their battle cry in cut scenes.
I'm sure i can think of more, but i gotta get back to work.