In the scene when Arnold is riding the his motorcycle to save the red haired kid from getting hit by the truck, T-1000 is driving. There's one scene where the biker, "Arnold", has to jump off a little thing to get into the waterway. When it shows this scene, you can clearly see who is riding the bike off the ramp. It's really funny, because as we all know Arnold is pretty ripped. When you look at the rider coming off the jump, you see only his face, and it's quite the chubby man.