Complex sentence: Stewie, Brian, Chase, and Aykroyd try to warn Mayor West, but they discover that the mayor is a sleeper agent when Aykroyd inadvertently uses the trigger phrase.
Split into simpler sentences: Stewie, Brian, Chase, and Aykroyd try to warn Mayor West. They discover that the mayor is a sleeper agent when Aykroyd inadvertently uses the trigger phrase.