This is about a friend of a friend who has a 4-year-old boy.
Recently they went to the zoo. The boy got lost, and when the mother found him after 45 minutes or so, he was crouched in a corner, clutching his backpack. He insisted on going home, and not even the promise of a visit to the toy shop could lure him. He just wanted to go home and have a bath. Naturally, this freaked the mum out a bit - what on earth had happened to her little boy?
So, they got home and she ran him a bath. After a bit, she went to check on him, because she thought the splashing was getting a bit out of hand. Turns out he wasn't alone on the bath tub. A little penguin was keeping him company, having a grand time in the water. She rang the zoo, and they said not to worry. Apparently this penguin was very friendly and liked to take field trips. It had been hidden in the boy's backpack for the whole time it took for them to get home from the zoo. They said to simply drop the penguin back to them the next day. And I am not making this up!