The Monkey-Doodle-Do in the 4 Marx Brother's The Cocoanuts (1929). Here it is in situ sung and danced by the delicious Mary Eaton:

http://www.youtube.com/watch?v=8P9rQs3F9vw

And here it is used as the soundtrack for a film of a monkey in Edinburgh Zoo playing with a dead mouse I made back in 2004:

http://www.youtube.com/watch?v=atN8qQfcsGc