"Only if it turns out that reality is actually nothing more than a holographic illusion created by the interplay of subatomic particles on a vast two-dimensional membrane."
This article covers a subject that has been deemed non-canon by either the author or the Back to the Future licensees, and thus should not be taken as a part of the "real" Back to the Future universe.
The electric perpetual portable trampoline was an invention that Doc Brown gave his son Jules to help him get exercise. In 1991, Jules used it to get Marty McFly out of a tree after he was chased up there by Doc's sick dog, Einstein.
Marty couldn't get off the trampoline until Doc pushed the button to disable it, after which it folded up, and Marty fell to the ground.
