I'm one of the ten people on the planet who don't watch The Simpsons, so I'm not even sure who Groundskeeper Willie is. But Alex played himself. Along with the members of the New Orleans Nightcrawlers.
One of those Simpsons guys hangs around town a lot.
An atheist was rowing on Loch Ness in Scotland one day, when suddenly the Loch Ness monster attacked and grabbed him from his boat. He panicked and shouted "God help me!", and suddenly, the monster and everything around him just froze. A voice from the heavens boomed "You say you don't believe in me, but now you're asking for my help?" The atheist looked up and said, "Well, ten seconds ago I didn't believe in the Loch Ness Monster either."