I love listening to the little nuances of people's speech and voices. I've always been able to mimic people. I do different voices for different characters in books for the kids but my kids especially like that I do Elmo, Kermit, Gonzo, and Miss Piggy. They have me sing bedtime stories in character. My son likes to hand me different stuffed animals while I'm singing to have me change my voice throughout the song.
They recently have requested Fozzie Bear. That's going to take some studying for me.
My husband does.. all the time. He is really good at it. He can also hear any voice from almost any celebrity (such as a voiced-over cartoon) and know who it is. It's really amazing.. I just wish he could make some real money off of it :P