The lifecycle of pajamas

Ben has taken to wearing only underwear to bed.  This is fine by us except for when he gets his "pajamas" on at 6pm and then comes down to watch a movie with us on the couch.  Here is the conversation from the other night:

Mommy: Ben, what's with the underwear?

Ben: This what I'm wearing to bed.

Daddy: well, how about some shorts?

Ben:  I tried that and it was OK, but this is how it goes:  ONE - top and bottoms for pajamas.  TWO - Only shorts for pajamas.  THREE - Only only underwear and your skin is soft on the sheets. THAT is the life-cycle of pajamas!

Mommy:  Who can argue with that?