My Future Self 'n' Me
"When a 32-year-old man claiming to be Stan from the future shows up in South Park, young Stan is forced to come to terms with the loser he will become. Meanwhile, South Park's own little entrepreneur, Eric Cartman, is at the helm of a new money-making venture. Cartman is in the business of revenge." - The South Park website
And that means we have to remove an episode from my favorite-15 list so let's get rid of I'm a Little Bit Country. And My Future Self 'n' Me should definitely go way higher up in the list.