What The... ?!?!?

We have this nifty mesh cover for the pack n' plays, so that we can sit outside without worrying about mosquitoes... and I had it stashed in the inside corner of said pack n' play, ready for action. The kids were playing in the part of the kitchen that we've kid-proofed while I paid bills at the computer. I was maybe 7 feet away. Things were going swimmingly until I hear Caden laugh one of his big-ole-guffaw-style chuckles. Which got me wondering, what could be so funny...