The Simpsons S37 E14 Irrational Treasure [800th episode]

"Just a product of society that's lost its good manners."

Marge's crusade to get the family dog in better shape leads to her entering Santa's Little Helper in canine agility competitions and a trip to the National Dog Show in Philadelphia. There, Marge and Homer suddenly find themselves - and the dog - mixed up in a historical conspiracy adventure worthy of a "National Treasure" movie.