Calvin and Hobbes

Calvin and Hobbes is a classic comic strip about a boy named Calvin and his stuffed tiger Hobbes, who comes to life when no one else save Calvin is around.

Badfic
It is not unheard of for a tiger Mary Sue to steal Hobbes' heart.

Cardboard Box Technology
Calvin's cardboard box can serve as a Duplicator, Transmogrifier, or time machine. The orientation of the box indicates which is which: Open side up means a time machine, open side to the side means a Duplicator, and open side down means a Transmogrifier.