The Invisible Box

Last night, after watching an episode of "Phineas and Ferb", Maggie & Daddy played the "invisible box" game. They would point at each other and say "Zap! You're in an invisible box!" A little later, while Maggie was sitting beside me, Daddy put us both in an invisible box and the conversation went a little like this:

D "Zap! I put you and Mommy in an invisible box!"
M "Oh, no! I know, I'll make an invisible door!"
D "I put an invisible lock on the invisible door."
M "Hmm. I know! I have an invisible key to unlock the door!"
D "But there's an invisible dog outside. And he won't let you get out."
M "I have an invisible treat for the dog. And he won't get me."
D "I put an invisible dinosaur outside!"
M "I will get on his head and he will let us down."