GET SHORTY ***½ (Starz on Comcast) Sprightly comedy based on the interchangeability of movie producers and mobsters - smartly written and juicily acted. John Travolta, in full comeback mode, plays a cool thug who goes to Hollywood to collect on a debt and decides it’s time to change careers. Delicious support from Gene Hackman as a shlockmeister, Rene Russo as a disillusioned scream queen, Danny DeVito as the fickle little megastar of the title, and Delroy Lindo as local muscle who also wants into the movie biz. (R; runs through Aug. 4)