In this trick, David Blaine takes Katy Perry's purse and promises he will pull a bunny out of it. He reaches into the purse and pulls out ... an aligator! Talk about a surprise!
You can see this funny and shocking illusion here:
The aligator was hidden under the table. It was probably put there by a member of Blaine's team before the filming began. Blaine then conceals Katy's view with the purse while pulling the aligator from behind the table, making it look like he's pulling it out of the purse. The camera is positioned in just the right way so this isn't visible to the TV audience either.
It's really quite a simple trick, but made more powerful by the element of surprise. Blaine says he will pull out a bunny, and you are expecting a bunny, but then suddenly ... an aligator appears!