Continuity mistake: When Billy frees Gizmo, the pen on the desk changes positions between shots.
Continuity mistake: Whenever a complete image of Gizmo appears walking or dancing, the puppet is 10 cm taller and way chubbier than the one commonly used. For example, when he dances in the lab, count the metal squares in the cage: He grows from a height of 6 to 9 between shots.
Continuity mistake: When Clamp visits the office, there's a man with grey hair walking from the right side of the screen. A frame later he's moved 15 meters to the left.
Continuity mistake: When Futterman throws the gremlin onto the cement, before moving the slide, the Gremlin's neck and back have no cement, but a frame later they're totally covered in it.
Continuity mistake: When Forster is seduced by the Gremlin, his hand alternates between being on her shoulder or on her back.
Continuity mistake: When Gizmo dances in the lab, the position of the cage door, and the distance between the door and Gizmo changes between shots.
Continuity mistake: When Futterman is being attacked by the Gremlin, his wife is on the right, a frame later she is standing on the left side, several meters away.
Continuity mistake: After Clamp kills the Gremlin the desk is clean. A frame later, when Billy shows up, there's a gallon of goo all over the place.
Revealing mistake: When Clamp has the Gremlin attached to his chest, his left hand is very obviously puppeting the Gremlin's arm. Clamp's fake arm is very long and makes a weird twisted bend around the Gremlin's back.
Continuity mistake: When water falls on Billy's desk, a small squared object next to the pens keeps changing positions between shots.
Continuity mistake: The lettuce leaf on Forster's shoulder changes shape between shots.
Revealing mistake: When the female Gremlin jumps on Forster, his arm is obviously controlling the puppet. His fake arm's awkward position plus a fake chubby hand reveals it.
Revealing mistake: In the kitchen, Crazy Gremlin throws an ice cream at Kate, which doesn't produce a stain and bounces around, revealing it's a rubber prop.
Continuity mistake: Amount of green flesh on Clamp's face and suit when killing the Gremlin disappears / reappears.
Continuity mistake: When the old man is fixing the water fountain, a towel appears / disappears between shots.
Continuity mistake: After water falls on Billy's desk, the table and floor appear totally dry.
Answer: She only saw him briefly, never in full light either. Plus, it was some time ago. I don't think she would suspect there is another one either.
lionhead
At the end of the first movie, after killing the gremlins, everyone is at Billy's house, and Kate puts a thermometer in Gizmo's mouth and looks directly at him while doing it, giving her plenty of time to look at him.
Still, very briefly, still in low light. She has had way less interaction with Gizmo overall.
lionhead