S18E20: Stop or My Dog Will Shoot!

In the episode "The Simpsons - S18E20: Stop or My Dog Will Shoot," things get predictably chaotic when Santa's Little Helper becomes a local hero after he helps the police capture a criminal. Naturally, Springfield being what it is, the family enrolls him in the police academy, where he becomes a certified police dog. Homer, being Homer, can't help but get himself into trouble. He gets trapped in a corn maze during a family outing, and it's up to Santa's Little Helper to save him. After quite an adventure involving a lot of corn and not much sense of direction, the heroic dog tracks Homer down and rescues him. However, all good things must come to an end. Santa's Little Helper starts acting aggressively due to the police training, and after scaring Bart, the family decides it's time for him to retire from the force. The episode wraps up with Santa's Little Helper returning home, back to his regular, slightly less heroic but much-loved dog self.