Back to the Future is a story of time travel, moral lessons and a dangerous lunatic who nearly destroys the universe on three separate occasions and nearly kills the underage boy he hangs around with on at least five others.
Doc Brown first tested his time machine on his own dog and was visibly surprised when it actually survived. Other highlights include nearly running himself over by remote control, using a date-rape machine on Marty's girlfriend and accidentally creating an entire dimension of hell.
This is why he was controversially cast as Commander Kruge in Star Trek 3. While most were baffled at the choice of a comedic actor, director Leonard Nimoy recognized an actor who could portray destroying an entire world without giving a rat's ass.