Complex sentence: Emmett Lathrop "Doc" Brown, Ph.D., is a fictional character in the "Back to the Future trilogy" in which he is the inventor of the first time machine he builds out of a DeLorean sports car.
Split into simpler sentences: Emmett Lathrop "Doc" Brown, Ph.D., is a fictional character in the "Back to the Future trilogy". He is the inventor of the first time machine, which he builds out of a DeLorean sports car.