"Master Chief Sucks at Plot Twists" is the tenth episode of season 3 and the penultimate episode of the series.
After a short "previously" segment, Master Chief, the Arbiter, Cortana, and Johnson find themselves unable to reach Building 69, as they need a boat. Master Chief commissions a pirate to take them. When they arrive, they see the Halo ring explode up in space, and moments later, Ronald appears to tell them the King is dead. They find Building 69, a giant glass tower in the middle of the ocean, and enter. Ronald prepares to download the program for his dummy AI, only to be told it has already been downloaded. Suddenly, the King himself appears, alive. The Arbiter accurately guesses he is an AI, and the King says he has finally reached his goal and downloaded the program. Then he explains his true plan: Master Chief's video series is scripted by a force beyond their control for the entertainment of the "real world." The King says he can now take on that force and free them from their fictional world, but Ronald says the King really wants to conquer the real world and the show's viewers. The King proceeds to demonstrate his powers by disintegrating Ronald. Johnson tells the others to run while he holds off the King in a duel, and the King reveals the truth to Johnson: that he is Johnson's old friend, Caesar Charlemagne. Johnson is shocked to hear this, but still refuses to help him, and he is destroyed. Having escaped, Master Chief and the Arbiter wonder what to do next, and Cortana says she met someone in the AI database with a grudge against the King who can help them. As they wonder who it is, CATS appears.
- The title refers to both the plot twist of the King being the true villain, and the plot twist that CATS has returned to help the heroes.
- During the end credits, fight scenes featuring each of the characters are displayed. The episodes the scenes are from are "Master Chief: The Second Finale" (Master Chief, the Arbiter, the King), "Master Chief vs Hillary Clinton" (Cortana), "Master Chief Sucks at Ordering Burger King" (Ronald, Johnson), and "Master Chief: The Finale" (CATS).
- As of this episode, every recurring character in the series is dead.
- After the credits, a title appears revealing the series will conclude on May 8, 2010.
- Scenes from this episode were first previewed in the trailer for "Master Chief: The Secret Origin of the King."
- The Internet meme song "You are a Pirate" from the children's show LazyTown plays during the pirate-themed transition to Building 69.
- The King revealing his true identity to Johnson is a parody of the famous reveal from Star Wars Episode V: The Empire Strikes Back.
- When Cortana reveals the person she has met who can help them, their old enemy CATS, the scene is a reference to the end of Pirates of the Caribbean: Dead Man's Chest when the group's old nemesis, Captain Barbossa, is revealed as their new ally.
- The group's new ally is none other than their old nemesis, CATS, who was previously thought to be dead. ("Master Chief: The Finale")
- Cortana says she met their new ally while she was imprisoned in the AI database. ("Master Chief Sucks at Rescue Missions")
- Ronald mentions how he killed the King and the group sees the Halo ring explode from Earth. ("Master Chief: The Secret Origin of the King")