Sometimes Opposites Don't Attract

Conversation participants:
Daddy (Age 32)
A.J. (Age 3 1/2)
Location: In the den

A.J.: Daddy, me and Mommy were playing 'Opposites'. Do you want to play with me?
Daddy: How do you play 'Opposites'?
A.J.: Well, I say something and you say the opposite.
Daddy: Okay.
A.J.: Clean!
Daddy: Dirty?
A.J.: That's right. Okay...big!
Daddy: Little?
A.J.: That's right! Umm...hippo!
Daddy: You want me to say the opposite of hippo?
A.J.: Yes!
Daddy: I don't know...rhino?
A.J.: No! It's sword!
Daddy: I should have known that.