So basically you just put one of your hands under your bed sheets leaving a finger peaking out just a little
Wiggle your finger a bit as bait and your cats eye pupils will grow full size and he will try to sneak attack your finger. Since cats are predators it's a fun little catch the prey game for them. When your cat sprints out for the catch quickly reposition your finger and repeat until your cat gets tired. Or eventually let your cat catch your finger. Your cat might scratch you though so beware