Peacock - based off the clues, I thought it was going to be Wayne Newton, but once he started singing, I thought the same thing JunkHead did: David Hasselhoff
Hippo - I thought it was a basketball player. My guess was Blake Griffin, but I was obviously wrong.
Monster - No clue. Based on the clues, I was thinking Vanilla Ice, but the voice didn't match. And the "I'm a singer, but only to some" clue really sticks out to me. So my two random guesses are Keenan Thompson or T-Pain.
Unicorn - Paris Hilton
Deer - Peyton Manning
Lion - I had no idea when I watched it. All I knew was that was a chick with really thick thighs...probably a black woman. But then my mother-in-law called and happened to ask if we watched. She said she knew who it was & why, and I'm 100% sure she is correct. - Rumer Willis - She apparently has a lion tattoo on her arm, has 4 sisters, and of course is the daughter of Bruce Willis & Demi Moore