Back to the Future: The Enchantment Under the Sea Dance Revisited (Google Video)
Back to the Future and Back to the Future II are brought together in this composite clip by Cloudy Eden Productions (no website yet). Clips from the two movies are sequenced and shown in two subframes in order to illustrate how the same moments in the plot were shot and edited in the original and the sequel. There are some confusing segments when a subframe goes black due to the fact that the films themselves are not in perfect sync in real time. The occasional appearance of a third subframe also muddles things even if it enlivens this clip itself a bit. When everything comes together here and there, though, it all works quite well and brings together the two films in an entertaining way.
Via MetaFilter. Also check out this Ask Metafilter thread on time travel.

awesome!
ahahahhahahah
that's indredible
wery good job
johny b. goode!
Posted by: Joe Cool | Monday, August 13, 2007 at 11:39 PM
Wow, nice job. It does point out a continuity error in the movies...if Strickland was looking out the window of his office at that time, then he would have seen Biff's gang grab Marty and Biff accosting Lorraine.
Posted by: Mark Smart | Tuesday, November 20, 2007 at 06:50 PM