Song within a song

Anyone know of any songs where there are bits and pieces of other songs within the tune either as an opening or thrown within the song or a new song based around a theme from another one? For example, Dark Angel's Psychosexuality opens up with the riff from Misilou made famous in the Pulp Fiction soundtrack which itself is an old song from Greece. Or Mortification's Jaws of Life which rips off the Jaws theme song?

The new David Gilmour single is based off the tones played before announcements at French train stations.

Sacred Reich's "Surf Nicaragua" uses some of the music from the song "Wipe Out".

"Ein Heller und ein Batzen" at the beginning of "Fast As A Shark."

This happens frequently in jazz during solos, the soloist will often quote a piece of a melody during their improvisation, sometimes for comical effect (like mixing in Happy Birthday in the middle of a sax solo).

Then of course there's Scatterbrain and "Down With The Ship" which contains riffs from a ton of different songs:

The James Gang - Bomber

The instrumental mid sections contains pieces from: Ravel's "Bolero" and Vince Guaraldi's score for Cast Your Fate To The Wind

S.D. wrote:

This happens frequently in jazz during solos, the soloist will often quote a piece of a melody during their improvisation, sometimes for comical effect (like mixing in Happy Birthday in the middle of a sax solo).  

Then of course there's Scatterbrain and "Down With The Ship" which contains riffs from a ton of different songs:

No way! I was actually telling my wife about this song last night! While we were waiting for Whitesnake to take the stage, the house music was on and it was some weird techno mash up of James Brown songs with the riff from Zep's "Whole Lotta Love" and the breakdown from "Heartbreaker" somehow worked in. When she remarked about the music I told her about Scatterbrain.

Woke Up This Morning by Alabama 3 which features loops from Howlin' Wolf.

I don't think Budgie were ever given credit for this bass riff:

The Devil's Triangle by King Crimson is really a rock rearrangement of Holst's "Mars".