Heh heh, La Texican. I'll never forget the mortified look on my son's face when he started doing the scream-and-slither-to-the-ground one night at the mall (we were leaving without getting him ice cream IIRC) and I dropped to the floor, wailing at the top of my lungs. He tugged at me to get me to stop and stand up, but I kept at it so he'd really get the message. He was two, I think. He never did it again.
I'm definitely seeing a strong tendency in DS5 to want to be seen as grown-up. It applies in lots of ways. He will refuse to spell "baby words", for instance, which to him is any word that doesn't meet some internal criteria of length, or uncommonness, or those in combination. When I pushed a bit to make sure he knew the words he was skipping, he always did, so I let it go. I've done my best to do more things with him lately to show that I understand that part of him. I recently gave him his first pocket knife; he doesn't have to hold my hand when we walk in the parking lot; I let him use the stove by himself; etc.
He came home the other day saying someone at his school was a "stink-ass" or "stank-ass" or "punk-ass", I can't remember which. I was too busy snickering to make a plausible fuss about it. He knows a lot of fun language-- for a while "jerkwad" was a fave, because of Bender from Futurama. And he probably knows I won't censor him, after I stood up for him at the playground one day, against a Christian mom who was aghast that he'd dared to say "hell".