Which one of these doesn't belong?

One of my friends had 9 baby bunnies born the day before our kittens. She brought them over today for us to see. We had a blast getting all the babies together.

We had put all the bunnies in the kitten box and then Mama jumped in. She just looked around and laid down. She definitely knew they were different, but she actually licked a few. She didn't seem to care one bit.