S9E2: The Principal and the Pauper

In "The Principal and the Pauper," we discover that Principal Seymour Skinner is actually an imposter named Armin Tamzarian. The real Seymour Skinner, a war hero presumed dead, returns to Springfield and reclaims his position as principal of Springfield Elementary. Armin is kicked out of town and tries to start a new life, but the townspeople quickly realize they preferred the imposter to the real Skinner. They bring Armin back and send the real Skinner packing on a train, never to return. The episode wraps up with Judge Snyder decreeing that no one will ever mention the incident again under penalty of torture, effectively resetting the status quo.