I thought the nanny episode was so funny. He really is the ultimate brat, so spoiled and manipulative and causes so much trouble.
After even the supernannies can't handle him, it was a dog trainer who put him in line. And how Cartman was yelling how he wasn't a dog as he jumped up and down for a piece of fried chicken. We all know how cruel Cartman is to the point of being a sociopath, and this line is great:
"I don't understand why you became a nanny. If you love children so much, how come you're not a mommy? You're sterile, is that it? No, that's too convenient of an excuse. The truth is nobody ever wanted to have babies with you, isn't that it? Always the mom's maid and never the mom? Must be hard on you, knowing that the years are ticking away, your friends all getting married and all the while your uterus is slowly shriveling away, drying up, becoming totally worthless. Yes, let the anger come! Strike me down while you can, but it won't make your dried-up ovaries any more fertile!"