When the leprechaun climbs down the chimney and Nathan shoots him, he falls near the connecting room. The following shot from above shows him now to be in the middle of the room.
Deep Roy, Warwick Davis's stunt double, is much taller than Davis. It's very noticeable when Roy is used in a scene.
At the coin shop, the shop owner's suspenders alternate between being hooked in the back and not being hooked. This happens just after Alex and Ozzie leave for the restaurant.
Near the beginning of the film when Tory first meets Nathan, he is alternately behind the jeep and resting his arms on the extra gas cans on the bumper.
When the leprechaun chases Tory around the nursing home, his arms turn the wheelchair wheels very quickly in the long shots. In the close-up shot of him in the chair, his arms are moving at normal speed.
The explosion in the well is totally out of proportion to the amount of gasoline used, and much bigger than it should be. In addition, being that the well has a large opening, the explosion wouldn't blow the stone walls of the well apart.
At around 58 minutes, the Leprechaun busts the truck's windshield. A front windshield doesn't shard the way that it does in the film and instead would just crack as it is made of safety glass.
After J.D. is bitten by what he thinks is a cat, the shot of the leprechaun in the hole is an image superimposed over the hole with daylight shining behind him.
The buckle on the leprechaun's hat is glued on. If it were designed to look like a real buckle, the center bar would not be visible.
When Tory rips the phone from the wall you can see that it was attached to the wall with only a screw which is still in the wall. However, no connecting phone line is visible on the phone nor is there a plug socket on the wall for a phone line.
When Tori heads out after the Leprechaun with a shotgun it is late at night. But daylight is clearly seen through the kitchen windows.
When Tory enters the hospital she comes across the sleeping security guard. She takes the folder detailing room numbers from under the notepad and places the notepad back on the desk in a central location. However, when Tory places the room number list back on the table, the notepad has moved to the left edge of the desk.
When Tory finds the cop in his car and hits the leprechaun in the eye with the police baton. The cop isn't supposed to have it since he threw it earlier.
When Tory runs away from the Leprechaun in the well scene, you hear her crying "Oh God!" But when she turns around to look back, her mouth isn't moving, and she's not as distressed as the sound would suggest.
When Tory finds the cop in his car.