I think Jimmy actually has cerebral palsy, where you're brain works fine but your body is failing you... hence his comedy act and obvious high intelligence. I think people have a kind of love/hate relationship with themselves for laughing at stuff like that, but in one sense it's irony, parody, etc. On the other hand, if you have that affliction or your loved one (child, sibling, parent) has that affliction (or any affliction), making fun of it isn't funny at all.
Timmy seems more mentally impaired.
EVERYBODY on that show has severe problems (especially Eric!!)
Either way, I like Butters and Tweek (esp when Butters puts on his super-villain mask and adopts that alter-ego). Also, if you haven't seen "Team America: World Police" (with the marionettes), that's HILARIOUS!
And yes, milk snakes grow. They don't get as huge as Rat Snakes or some other species, but I'm guessing it'll top out around 3 feet or so. I'll keep posting as he grows...
Walt