Weird Science
Yes, that is Bill Paxton as Ilan Mitchell-Smith's militaristic big brother. And that's Robert Downey Jr. as one of the in-crowd jerks who makes nerds Mitchell-Smith and Hall's lives miserable. Fortunately, this is a John Hughes comedy and our smart nerds create the perfect woman, Lisa (Kelly LeBrock), using a computer and voodoo. Lisa is a willing sex toy, has magical powers, and just wants to help the boys get even and meet nice babes. She even cleans up. The fantasy ebullience of Hughes is given full rein here and that's good and bad (mostly good).
