Sam's back from Hell, and Dean makes a pop culture reference during a conversation at some point. Sam's all "What?" and confused, because 120 years is a long time to go without seeing any movies. So it's up to Dean to reintroduce him to all the best parts of pop culture. Between hunts,
they have movie marathons, and slowly Sam relearns Jurassic Park, Back to the Future, Die Hard, Star Wars...