I can safely say it is the only show on TV where there has never once been an episode that didn't cause me to laugh out loud at least once. Seeing how long it's been on, that takes some doing. I've been lazy of late though and have missed the new ones. I'll have to catch em on the southparkstudios site.
Also, I may have to agree that imagination land has some awesome scenes. Also of note are Aspen, D & T (vote or die), Scott Tenorman must die, and as previously noted, dog whisperer.