I’m a cow by RMT. http://www.pendland.com/html/cow.html
Honestly, are there any songs that aren’t improved by the addition of flying Viking kittens? 
Maggie Estep has some funny… are they songs? Is she rapping? Is it just poetry with some music behind and a little singing? I don’t know. But “Emotional Idiot” and “Stalk Me” crack me up.
I think the funniest song is Alice’s Restaurant by Arlo Guthrie. Keeps you laughing for over 18 minutes.