You know that feeling when you're watching a movie, and something looks eerily familiar? It's not that filmmakers are incapable of being original. It's that they can't resist adding little tips-of-the-hat to other movies. Sometimes it's acknowledging influence, sometimes it's the filmmaker saying "Hey, don't forget that other thing I did!" And sometimes it's just a random shout-out.
Whatever the reason, they're easy to miss, fun to look at, and a thousand percent on-purpose. For example:
Source: Film School Rejects