This are two charts created by @Jishai showing the voice actors that work for the Simpsons and South Park and all the characters they play. Eight Simpsons voice actors play over 100 characters, with the top three playing 73. South Park's Trey Parker plays a whopping (possibly a double whopping with cheese) 32 voices. Me? I have two voices. I have my regular voice, and I have the one I use when I want to sound like a sexy lady. *ahem* Hey big boy -- wanna go for a ride? "You sound like gravel in a garbage disposal." So the ride is probably a no-go is what you're saying.
Keep going for the South Park version but you're better off checking out the high-res version in the link above.
Thanks to Francisco, who threw his voice in his email and totally made me think he was someone else. You're tricky!