Why won't you just sleep?

For the past four days, Spencer, my most of the time cute as a button (takes after his mom) 19 month old has decided that life is way too exciting for him to miss any of it, especially by sleeping. So this results in an extremely crabby baby who wails like there is someone dissecting him every time we put him down for a nap, or even at night. Just out of the blue. I'm sure it is just a phase, but it really sucks. God I'm glad to be back at work.