Songs/Movies that reference other songs/movies

I love when songs or movies reference other songs or movies. It sort of feels like an inside joke, as long as you know what they're referring to. Some examples include:

1. Jason Aldean's song "1994" : This song is all about going back in time to 1994, when Joe Diffie was the country singer of choice. Now, if you don't know who Joe Diffie is or haven't heard any of his songs, then "1994" is just another country song to you. But if you DO know who Diffie is, then you get the references in "Your new favorite color is John Deere green" and "So help me girl I'll be your Pick-Up Man." These make the song that much more fun to listen to!

2. Julia Roberts in Valentine's Day: I can't remember if this was actually in the movie or in the deleted scenes, but at one point, Roberts is in a taxi, and the taxi driver mentions that they are on Rodeo Drive, and asks her if she's ever shopped there before. She says, "I did once, actually. But, big mistake. Big. Huge." If you've never seen Pretty Woman, then that means nothing to you. But if you have seen it, then you can't help but laugh out loud when she says that.

3. Star Trek Into Darkness: Since this new Star Trek movie is a prequel, it makes sense that there would be references to the original show/movies. But some of them are so obvious to those who have seen The Wrath of Khan, the second original Star Trek movie. Like when Kirk is stuck in the radioactive area of the ship: that SAME thing happens in the original movie, just with Spock in there instead. The audience won't see those parallels until they've seen the older movie first.

There are a MILLION other examples. Can you name any?