Dave the Gnome: Your program sounds a lot like "Star Search" starring Ed McMahon, which ran from 1983 to 1997. (Why do I waste so much time looking up crap like this?) Contestants on this show didn't have to dress up and imitate anyone in particular, but many did. Some eventually became famous (two that come to mind are Britney Spears and LeAnn Rimes), but most sank back into obscurity. And the ones who did become famous usually took several more years of hard work to do it. (I think Britney was about 10 when she appeared.)

McMahon now has a website called Next Big Star. For a small fee, you can have your own video posted on his site!

By the way, I wish I could find a website that does for TV what IMDb does for movies. It seems like there ought to be one. Anyone have any suggestions?