The animated spiders on Shrek. I am 15 and can't even look at them! LOL! Yes, I have a spider phobia, and the special effects (you see the spiders and then air blows to feel like they are running around at your feet.) may scare your kids a bit. Yeah, the stone dragon may scare them a bit. Red glowing eyes. Creepy.
Nothing I can think of on Jimmy Neutron...