Continuity mistake: When Billy shows Marla his new sketches she is holding a notepad and a briefcase. Her hand on the notepad change position between the shots. (00:10:00)
Continuity mistake: As Billy grabs Gizmo out of the cage he grabs him with both hands. When it cuts he only holds him with one hand. (00:19:55)
Visible crew/equipment: After Billy has grabbed Gizmo from the laboratory he walks into the men's room. When the voice says "I hope you washed your hands", you can see the camera man moving reflected on the wall. (00:20:35)
Continuity mistake: When Clamp introduces himself to Billy, Billy is holding a pen. The way Billy holds the pen changes several times between the shots. (00:22:55)
Continuity mistake: When the drawer opens and Clams asks what's up with the drawer, Billy says it opens automatically while having his hands in his pocket. When it cuts his arms are crossed. (00:23:15)
Continuity mistake: When Forster grab the painting from Billy, the way he holds it differ between shots. (00:25:25)
Continuity mistake: When the waiter presents the chocolate moose, he holds and empty hand in front of the moose. When it cuts a plate suddenly appear in his hand. (00:32:40)
Continuity mistake: When the Futtermans arrive at Billy's and Kate's, we see Murray standing in the doorway with the luggage. On his right luggage there is a paper bag lying on top of it. When it cuts the paper bag has moved over to the other side. (00:35:30)
Factual error: When the Security Guard in the pump room gets bitten on the nose, he starts shooting with his revolver (a SIX shooter). Count the bangs. He manages to fire SEVEN times. (00:39:45)
Continuity mistake: When the gremlins are throwing pans in to the microwave, the display on the microwave is reading 9:20. As the gremlin gets hit by one of the pans the display is off. When it cuts the display is back on reading 9:20. (00:41:25)
Continuity mistake: When Gizmo falls down the hatch he lands on the cocoons. As he land on the floor you can see some green slime on his chest. A few shots later the slime is all gone. (00:41:30)
Deliberate mistake: The elevator operated by gremlins starts ascending at around 5 stories per second, based on the floor readings. Yet when the elevator suddenly stops dead, Kate does not fly into the air caused by the huge speed change. (00:50:05)
Continuity mistake: When the gremlin drinks the brain hormone, it starts shaking knocking over the bottle. When it cuts the bottle is back up. (00:57:35)
Revealing mistake: When Henry Futterman is attacked by the winged Gremlin, most pedestrians just pass by, only glancing occasionally at Dick Miller's frantic performance, since the Gremlin was only inserted. Only when Futterman smashes the pest into the wet cement, the Gremlin is the 'real' thing. (01:02:35)
Revealing mistake: The Gremlin who throws the beaker full of acid has his arm operated by a stick, which is visible as he chucks the beaker. (01:08:05)
Continuity mistake: As the crazy Mogwi changes from a ball to an actual creature, a can suddenly changes position on the shelf above, though nothing touches it.
Continuity mistake: When Futterman walks backwards to avoid the flying Gremlin, the passers by are not consistent between shots.
Other mistake: Gizmo can't be exposed to sunlight, yet when the shop is demolished he walks out on the street. Note how he is walking past the shady part of the curb to the sunny part, suffering no harm whatsoever.
Factual error: Water causes Gremlins to multiply. But in a shot during a cooking show, the insane Gremlin (Daffy) pops up in a pot of soup, which is water based, yet he still doesn't multiply.
Suggested correction: There have been other times when mogwais and gremlins get wet and don't multiply suggesting it's water, not water based liquids. In the first movie for example when the gremlins are drinking beer and Gizmo gets licked by the dog without multiplying.
Character mistake: Given Billy still remembered and recognized him it seems strange Kate doesn't when she mistakes Daffy for Gizmo.
Suggested correction: Billy spent significantly more time bonding with Gizmo in the first movie - days and days. By contrast Kate had very little actual time with him.