For as much as I’ve read about Men in Black 3, I had no idea what the plot was, other than Josh Brolin impersonates Tommy Lee Jones and something about time travel and Shea Stadium and Will Smith saying, “Ah, hell nah,” until yesterday. Turns out, Jemaine Clement, a.k.a. Jemaine Clemaine in HBO’s much beloved “Flight of the Conchords,” plays an alien named Boris, who goes BACK IN TIME, non Huey Lewis & the News-style, to assassinate Jones for some reason.