Thank you all so much for the heartfelt and really, really funny birthday wishes and links. I've looked at maybe 20% of them, and can't stop laughing.
My younger son gave me perhaps the best present a mother of a 2 1/2-year-old could get: He refused to wear a diaper to drop his brother off at school, and stayed dry all day! Then he did the same thing yesterday! And wore regular cloth (not rubberized) training pants to drop-off this morning, too.
What if he potty trains himself, too, just like his brother did? It would almost make up for all the stretch marks.
Edited to add: OK, this almost made me pee my pants: Potty training manual (actually a flowchart)