Fan Casting "The Really Useful One" in Who REALLY Shot Mr Burns?

Skinner: Uh... you know... one thing I sh-... Excuse me for one second. Chalmers: Of course. *Skinner walks into the kitchen to attend to the burning oven, when an ear-piercing metal screeching shakes the room, followed by a deafening crashing noise and a violent earthquake. Chalmers enters the kitchen, and gasps in horror at the sight of a blue steam engine with a human face welded onto its front, looking glumly down at the bloody remains of Principle Skinner.* Chalmers: What the f- Thomas: Something bad is going to happen to Springfield! It's already taken my world, and it's coming for yours too! Chalmers: WHO ARE YOU, AND WHAT ARE YOU DOING HERE?! Thomas: Well, it's a long story...