The further adventures of Marty McFly (Michael J. Fox) and “Doc” Emmett Brown (Christopher Lloyd) take them from 1985 to 2015 and back, and then back to 1955 after a mishap in the future involving the villain (Thomas F. Wilson) creates a universe parallel to the one they left. The problem with all the time-travel high jinks, involving multiple versions of the major characters (a gimmick that Robert Heinlein handled much better in stories like “By His Bootstraps” and “All You Zombies—”), is that in order to make the plot even semiintelligible, writer Bob Gale and director-cowriter Robert Zemeckis have to turn all these characters into strident geeks and make the frenetic action strictly formulaic. (Significantly, the principal “romantic” interest, Elisabeth Shue, is knocked unconscious early on so she won’t interfere with the little-boy games, and Fox briefly playing his own sister in drag only adds to the rampant misogyny.) There’s a bit of fun in the 2015 section (although this notion of the future is more nostalgic and Disneyfied than genuinely speculative), but the shrill simplicities that follow become increasingly mechanical. By the end, you may feel that you’ve just sat through a feature-length commercial for both part one (which has to be seen to make this sequel comprehensible) and part three (a trailer for it literally ends part two), along with a host of other consumables (from Pepsi to other Spielberg productions), and have been turned into a first-class geek along with the characters—an airhead consumer designed to wolf these products down. Please, Mr. Spielberg, give us all a break (1989).