It's the Anvilania National Anthem. From Animaniacs, show #10 (IIRC), "King Yakko". Something of a sendup of Duck Soup.
Since the national anthem, sung by Perry Coma, tended to put everyone to sleep, King Yakko sent a trojan anvil into the middle of the enemy forces. Once it was suitably placed, the anvil popped open and Perry Coma began singing, causing all of the enemy forces to fall asleep.