There is no such isotope as "Cobalt-40".
When Rat Fink starts duplicating himself in the lab, he says he will continue "dividing himself". Actually he is multiplying himself and not dividing.
In the beach make-out scene where the band is playing, several extras behind the band wave at and even flip-off the camera.
When the hearing-aid explodes the explosion clearly emanates from the floor, not the hearing-aid itself.