Visible crew/equipment: Whilst Dignan is leaving the motel, Inez gets Rocky to say to Dignan "Tell Anthony, I love him", to which Dignan says "All right, man, okay" and walks off. The following shot after this is of Dignan walking past the side of a building. Right at the start of the shot, for a split second, the reflection of the cameraman can be seen reflected in the window beside him. (00:48:45)
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.