This is what happens when you refuse to lie down

The other day James fell asleep in the car at noon and slept 30 minutes. Even though it was his second nap of the day (he slept 30 minutes earlier that morning) I decided there was no way he was going to make it to bedtime from 12:30 on only an hour total of napping. So at 3:30 I tried putting him down. Normally while I nurse him he gets sleepy and groggy- not this time. I put him in the crib wide awake but knowing that he needed to try to nap.
He played and fussed for a good 20 minutes before getting increasingly upset at being stuck in his crib. Finally the fussing stopped momentarily, then started again, then stopped, then started and on and on. I decided to peek in and see if he was finally going to sleep or if he had given up fussy and was playing. If the latter I decided it was almost getting too late for a nap and would get him up.
I looked peeked my head in and saw him...sitting up in the corner of the crib facing the doorway to our bedroom holding on the bumper...asleep. And as I watched I finally understood why I was hearing intermentent fussing. He was sitting up asleep but as his body truly relaxed he was starting to fall over and that was waking him up enough to straighten back up and he fussed being woken up. I watched this happen a few times while covering my mouth to suppress my laughter. Finally I decided it seemed like he wasn't going to fall fast asleep with this viscous cycle going on so I went in and tried to lay him down.
He was furious and immediately popped back up into a sitting position. I tried lying him down and patting his back a few more times but each time he popped back up. Finally I picked him up and rocked him until he was calm and laid him back down- obviously he needed the nap since he was tired enough to fall asleep sitting up. But as I left the room with him crying at me he was already sitting in that corner again. I left him hoping he'd fall asleep and finally he did. The above pictures are how I found him when I checked on him. When he woke up just 25 minutes later he had the imprint of the bumper seam going across his cheek and forehead.
Next time this happens I hope I can get it on camera!