You Can't Kiss It

I hear a loud thump coming from the bathroom, and, knowing that Calvin (my four year old) is in there, I run to see what happened. The following is a word for word re-enactment of what came next.

Me: (Seeing Calvin laying on the floor with his pants around his ankles with a cry-face on) Calvin, what happened?

Calvin: I was going to the bathroom and I slipped and fell down.

Me: Are you okay?

Calvin: I hurt my bottom...but you can't kiss it.