This toy has been in our house since Diego was a baby. We call it the pet gorilla.
It's just a picture of a baby gorilla that I downloaded, printed, cut out and stuck in an old candy box. Occasionally, we "feed" it some fresh bamboo, which adds to the effect.
Julio is fascinated.
He stares at it for a while, then asks for the box to be opened. He takes out and examines the bamboo and the picture. He says, "Gorilla!"
The other boys still occasionally play with it, but I remember that when they were his age, they were just as intrigued by it as Julio is now.