Visible crew/equipment: When a gremlin attacks the Mum from a Christmas tree, and the tree falls on top of her, you can clearly see a member of the crew with eyeglasses, wearing a red shirt, standing behind the tree pushing it forward on top of her. (00:54:30)
Visible crew/equipment: In the scene where the cop car flips over, if you pay attention, you can see the metal plate that's welded under the car that helps it flip over. (01:08:25)
Visible crew/equipment: In the classroom a Gremlin takes an apple, then eats it behind a desk. The Gremlin then throws it from behind the desk. Look closely and you will see the apple is actually thrown by a human hand, not a Gremlin hand. (00:48:00)
Visible crew/equipment: As Mrs. Deagle is walking along the street, carrying the broken snowman head, as she passes one store, clearly reflected, a little ahead of her, is a man carrying the boom mike. (00:10:00)
Visible crew/equipment: When Stripe is attacking Billy with the chainsaw, when the camera pans to the side right before Stripe attacks you can see a crew member's hand place Stripe over Billy. Also you will notice that there is a piece of plywood attached to Stripe's feet. (01:29:10 - 01:32:55)
Visible crew/equipment: In the bar, as one Gremlin bangs his beer glass on the table, you can see a wire attached to his arm, leading under the bar. (01:10:40)
Visible crew/equipment: Before Billy's mum pushes the gremlin into the microwave, you can see the top of a crew member's head, on the left of the gremlin, next to the microwave.
Answer: The original film was released before the PG-13 rating existed (it was one of the films responsible for its creation). Producers decided to remove some of the language and violence for the DVD release to avoid complaints about the PG rating.