I found a room full of Kittens. Look left on the log before jump towards the Vault. I used Ride the Lightning to get in. The Kittens are being trained to Assassinate Ogres. The orange one in the top left is Puss in Boots.
Some of you need to lighten up a bit
This room has been there since launch, Tirzah, one of our designers made it in her spare time over the weekend because she wanted to. The kid in that room is also hidden in 2 other spots in the world, try to find him.