I have no idea where he picked it up but James has discovered the low, evil chuckle (heh heh heh!). Picture a villian with a raised eyebrow looking at you over steepled fingers and you'll know what I mean. James does it in his little, hoarse voice pitched as low as he can and it usually follows the funniest sentances.
Today out of nowhere he said, "Mama, walk the plank! Heh heh heh." (Yes, we are still in a Peter Pan phase.) He followed it up with his mischievious smile.
I swear I am in trouble with this kid!