Sesame Street Mecha Builders Episode 4 Magnet Mayhem / Stop That Train Episode Title: Magnet Mayhem / Stop That Train Episode Description: The magnet crane at the construction site is switched on by mistake, sucking up all the metal in the area -- including Mecha Cookie and Mecha Abby! The Mechas learn about magnetism as they figure out how Mecha Elmo can stop the pull of the magnet before anything – or anyone! – else gets trapped. Then Mecha Elmo gets stick of the magnet too. Marwyn is waiting for an egg delivery at the Treetop Woods Train Station. When the engineer tries to stop the train, the brake lever snaps! The Mechas try different ways to stop the train without breaking any of Marwyn’s eggs.