While the leprechaun kisses Bridget, a fair amount of drool pours across her face. Immediately after there is no drool on her face at all.
Bridget bends the needle of the awl when she tries to stab the Leprechaun with it. It is bent differently when the Leprechaun picks it up.
Amount of alcohol in the hobo's bottle.
When Cody dunks Morty's head into the sink full of ice water, the ice cubes are NOT floating. Ice floats in water.
In the first film, Mr. O'Grady says that there is only one way to kill a leprechaun: a four-leaf clover, but in this film, wrought iron is used to kill the leprechaun. It is, however, never stated that this is the same Leprechaun from the first film. The fact that the Leprechaun was killed in the first film, supports this.
A direct quote from the first movie reveals the leprechaun's age to be 600 years, not 2000. It is, however, never stated that this is the same Leprechaun from the first film. The fact that the Leprechaun was killed in the first film, supports this.
Ian hears the Leprechaun's laugh in the garage, but does not hear the Leprechaun mocking him later on. It is possible that, taking into account Ian did not hear the sound of the lawnmower blades, that the Leprechaun's magic was so powerful that it blocked out any outside noise besides Bridget.
When the Leprechaun manifests an illusion of a topless Bridget, her skin tone and breast size change, indicating the use of a body double.
Wires are visible when the Leprechaun makes the slave float up in the air at the start of the movie.
As Cody gets chased by the Leprechaun on the go-cart, tire tracks made by the camera are visible, either side of Cody.
When the Leprechaun is locked inside the safe, the safe's interior looks larger than its exterior.
Prop finger when the leprechaun rips it from the man's hand.
In the beginning, when Bridget is waiting for Cody as he discusses the dark side tour, you can see people standing in the street and in the cars driving by watching the scene being filmed.
When Morty opens the safe, the Leprechaun touches the door to let himself out with no side effects.
After Cody gives the gold coin to the leprechaun disguised as Bridget, the boom mike is clearly visible directly over Cody's head.
After the Hearse is pulled over for running the red light, the Desk Sergeant lists one of the charges as "6 seat belt violations", but Bridget had stayed behind at the go-kart track, leaving only 5 people in the car.
In every other Leprechaun movie , the Leprechaun "punishes" those for stealing his gold. But in this movie he steals gold from other people with no problem.