Sesame Street Mecha Builders Episode 14 Cross That Bridge / Knock Knock! Who's There? Episode Title: Cross That Bridge / Knock Knock! Who's There? Episode Description: The train needs to cross the ravine, which becomes difficult when the Martians accidentally break the bridge. The Zee Mobile is great at counting the chickens at the farm, but won't stop crashing into and ruining MacBarm's barn door. While Zee performs some maintenance on the Zee Mobile, the Mechas use different materials to make a new barn door.