I thought, surely this is a fluke. He just happened to get his weight balanced well enough to get to his feet. It can't happen again. A 5-month-old doesn't just stand up. Well, today, he proved me wrong. A 5-month-old can just stand up. And, this time with one hand. (I promise no one did anything to help him!)
This growing-up thing is going way too fast. Thomas needs to take a break for a bit, I think!