When the cop starts kicking the Leprechaun, he kicks him with his right leg, but when the Leprechaun grabs his right leg and rips it off, they show that his left leg has been ripped off.
Rory's sunglasses when his girlfriend gets off the motorcycle and kisses him.
When Cedric is being attack by the leprechaun his headband disappears and reappears between shots.
When Emily finds the chest, the candle she is holding disappears at around 24 minutes.
The leprechaun chats on a cell phone to a girl. The girl hangs up and we hear a dial tone. Cell phones don't have dial tones.
After Watson Turns Jaime upside down you see that he has money in his mouth but when Watson and his crew leave there is nothing in his mouth.
When Rory's gun ran out of ammo, the slide would have locked back due to the follower in the magazine.
The cement at the end of the movie had too much water and would have been not as liquidity.
Rory said each coin weighed 8 ounces, and there were 200 coins to split between them. This makes the treasure chest weigh 100 pounds, although the characters were running with it as though it weighed nothing.
When Rory drives by on his motorcycle and hits the leprechaun that is attacking the woman he skids the back wheel when he turns around and you can see a tire track on the road from a previous take.