I used to joke with my wife that I thought that our son wasn't really mine, but if it were mathematically possible to be 1000% sure of something, then I'm sure that he's my boy.
During the course of teaching and playing Dungeons and Dragons with my son, I dumped out my dice bag into the tray and started sorting the sets. Tobias then pipes up, "I like sorting things... Why do you keep them all in one bag instead of separating them?" This caught me off guard, because I like sorting things as well. I had to analyze my actions before responding, "If I do it this way, then I get the fun of sorting EVERY time that I pull out the dice."
I know, it's mundane, but that kid cracks me up, and frustrates me all at the same time. It's like what I've always said... If I ever met my own clone, I'd want to kick my own ass, and then buy myself a beer.