They're cheap (free), all cats love them, they are great for kittens, and, when it's dirty, throw it away!

Pros: "affordable"

Cons: none

Lots of spontaneous fun times are had with shoe boxes! There's just never enough boxes at our house.

Pros: The price--free

Cons: boxes usually end up broke and cannot be reused

Our cats are too big to fit comfortably but they still squeeze into them. It's funny to watch

Pros: easy to come by

Cons: I think my wife buys more shoes just to get more of them

My cats have a blast playing in shoe boxes, actually they love any/all boxes, big or small

Pros: free/easy to come by

Cons: none that I have

My cat slept in a shoebox when he was a tiny kitten. He used it until he outgrew it.

Pros: cheap, easy to find

Cons: none