Complex sentence: When they find Chris has not absorbed anything from the trip, Stewie calls Chris a moron, angering him so much that he leaves and boards the RMS "Titanic" with Stewie's return pad, leaving them to board the ship to stop him.
Split into simpler sentences: When they find Chris has not absorbed anything from the trip, Stewie calls Chris a moron. This angers Chris so much that he leaves and boards the RMS "Titanic" with Stewie's return pad, leaving them to board the ship to stop him.