The trailer for the animated feature "Transformers One" has dropped. The prequel to the franchise, which stars the voice talents of Chris Hemsworth and Brian Tyree Henry, tells the story of a young Optimus Prime (Hemsworth), when he was just known as Orion Pax. Henry is D-16, before he became Optimus’ rival Megatron. Other cast members include Scarlett Johansson as Elita, Keegan-Michael Key as Bumblebee, Jon Hamm as Sentinel Prime and Laurence Fishburne as Alpha Trion. The movie hits theaters September 20.