Today, Martin made up his first joke (one that made sense, anyway):
Martin: Mom, do you know what rivers eat?
Me: You mean for lunch?
Martin: Yeah.
Me: No, what?
Martin: Fish.

And, apparently he's picking up some new phrasing around the house:
Me: Boy, what happened in the porch today?  It looks like a pigpen.
Martin: Certainly I didn't did it.  Of course, then I don't need to clean it up.