Complex sentence: They restart their trip when the conductor gets the caribou to move by pulling Smokey's beard, making him speak reindeer, but unfortunately, he, the boy, and the girl are stuck in the front of the engine.
Split into simpler sentences: They restart their trip when the conductor gets the caribou to move by pulling Smokey's beard, making him communicate with the caribou. As a result, the train is able to continue but unfortunately, the conductor, boy, and girl are stuck in the front of the engine.