Cliff from Cheers, Adam Sandler... I don't know a whole bunch of people. When he sings the Troll Doll themes as different bands he does a pretty good job too.
Found a short impression of Sandler...
http://www.youtube.com/watch?v=v1GUaMdy1Yc
Here's him singing about Trolls as different bands. Well, there's also some idiots lipsyncing along with it for some horrible reason.
http://www.youtube.com/watch?v=2CyIdOWRm2g