Charlies game.

We were taking a rather long trip, the almost four year old and I, when out of boredom he came up with this game: "daddy, what is one plus one"
Me: "two"
Him: "daddy, what is x plus x"
Me: "2x"
Him:"daddy, what is zebra plus zebra plus zebra"
Me: "3zebra"
This went on for several minutes, each time using different animals, people, numbers and objects. For every answer I gave him he let out a shriek and a giggle as if it was the silliest thing he had heard of.