As children's ghost stories go, Casper (1995, MCA/Universal) adheres admirably to its own internal logic. Unless Casper or another ghost clearly intervenes, the real world behaves as it normally does. But there is one eerily unexplainable phenomenon. That's the scene in which human shrink-to-the-spirits James Harvey (Bill Pullman) gets rolled up in a rug as he tumbles down a staircase. In his descent, his head is at the right side of the staircase. But when he hits the floor, his head and the rolled-up carpet have taken a 180-degree turn (allowing the carpet to photogenically unroll across the foyer). It's the type of inconsistency that can make anyone's head spin.