Stewie and the Dog are my favorites. The Dad keeps me amused as well, but not to the same degree.
My favorite episode was the one with Death in it. You know, where Stewie finally killed his mother, and because death was incapacitated, she didn't die.
This is very similar to the suggestion put forward by the Quirmian philosopher Ventre, who said, "Possibly the gods exist, and possibly they do not. So why not believe in them in any case? If it's all true you'll go to a lovely place when you die, and if it isn't then you've lost nothing, right?" When he died he woke up in a circle of gods holding nasty-looking sticks and one of them said, "We're going to show you what we think of Mr Clever Dick in these parts..."
-Terry Pratchett, Hogfather