I'm continually amazed by how the boys acquire little skills, so that I'm playing with them and then suddenly tweak "hello, how long have you been doing that?"
The example that prompted this was Connor's habit of insisting on having one of the train letters for his name when he's getting dressed after bath-time. I noticed he has awareness that he can hold it with one hand while I get his other arm into his sleepsuit, then he needs to swap the toy over from one hand to the other when I want to get the second arm into the sleepsuit. Clever!!