Continuity mistake: Bullet approaches the Jaguar with the two rich kids. He is leaning against the roof of the car, but in the close-up where he spits through the half opened window, he's leaning against the glass instead. (00:05:25)
Continuity mistake: When Janice and Guy are lying on the stairs of his loft apartment one of her shoes falls off. In the next shot it's back on her foot.
Continuity mistake: When Alex is walking around nude in just high heels watch carefully. They seem to come and go during the gun battle.
Revealing mistake: When the Leprechaun gets sucked into space, he grabs onto the edges of the cargo bay's doors. You can see pieces of his hands disappear into the doors, showing that it's CG.
Other mistake: In the unrated cut, during the bathroom sex scene, there are several very noticeable, unnatural jump cuts that make it clear where the extended footage was spliced in. Ex. Characters will suddenly move several inches instantaneously despite it being the exact same angle. While jump cuts can be used to artistic reasons, this is very much a clear case of unintentional "jumps" due to the footage being spliced in after-the-fact and there being a few frames missing.