Gary Lockwood, costar of Stanley Kubrick’s 1968 sci-fi masterpiece and psychedelic freakout 2001: A Space Odyssey, steps in for Keir Dullea, who was originally slated to appear at two screenings of the film this weekend at the Music Box. Lockwood plays Dr. Frank Poole, the less fortunate of the spaceship’s two human pilots, the one who (spoiler alert) doesn’t make it on the journey to the center of the mind. Dullea, who plays Dr. Dave Bowman, is otherwise engaged in the Dublin world stage premiere of The Shawshank Redemption

2001 screens Saturday in Rusty Nails’s third Sci-Fi Spectacular, a 14-hour movie marathon that includes The Incredible Shrinking Man, War of the Worlds, Planet of the Apes, The Brother From Another Planet, Aliens, and David Cronenberg’s The Fly. Tickets are $20 in advance at Laurie’s Planet of Sound, 4639 N. Lincoln, and $24 at the door. The festival runs noon Saturday to 2 AM Sunday. And 2001 plays again Sunday at 5:30 ($12), 3733 N. Southport.