Continuity mistake: When Max bites the Grinch in the mail room, and the Grinch starts spinning around, a pile of presents appears under the wall of mail slots between shots.
Continuity mistake: When the little girl first sees the Grinch the orange light is spinning around and you can hear a siren. Then when the Grinch speaks it conveniently turns off and back on again when he finishes.
Continuity mistake: In the wide shot that would be a view from the roof of Betty Lou's house, you can see the spool of lights on Martha May's cannon isn't lit up or moving.
Visible crew/equipment: The movie was filmed in a large set to recreate Whoville, but in the mayor's first appearance, if you look in Lou Who's glasses, you can see a stage light from the ceiling above.
Continuity mistake: When he's talking to Cindy Lou in the Post Office, Lou is riding on the movable ladder, When he says "You kids and the Grinch", he's right at the end of the track when the camera cuts to Cindy Lou. When it cuts back, he's just stopping at the end. The sound while the camera is on Cindy Lou suggested that the track was longer than it was.
Continuity mistake: In the scene where the Grinch is talking to the town after he flips out during the Whobilation,the mayor in the background switches from facing inward to his assistant to facing outwards.
Continuity mistake: The little car the Grinch commandeers and crashes after going on his rampage goes from having a little flame, to fully engulfed, and back before the explosion.
Continuity mistake: When testing his engines and after he hits the wall, he turns around and is leaning on the wall. He's tilted toward the "HIT HERE" circle. The camera cuts closer in, and he's now standing straighter in relation to the circle.
Continuity mistake: After the Grinch answers the cop's greeting with "Flatfoot!", two Whos carrying packages pass by him, and he watches them pass. As the Grinch approaches two Who children to give them the hacksaw, the same package-laden Whos pass by again.
Continuity mistake: When the Grinch goes to wrap Cindy, he grabs the end of the wrap with his right hand and pulls. Suddenly, he has both hands on it, and there was the sound of his left hand grabbing added in.
Continuity mistake: In the wide shot of the town square after the mayor says there "is no Grinch problem here!", the yellow car that had a full cab that the red car hit is missing, and the red car's right headlight that was knocked out in the crash with the yellow car is back in place.
Visible crew/equipment: While The Grinch is returning to his home for the first time that we see and after he says "one man's trash is another one's potpourri" while he's entering you can see the shadow of the machine that holds the camera up high behind him and Max.
Revealing mistake: As the saw cuts around the Christmas tree, before it falls through the floor, you can see a faint line where the saw tracks around to cut the floor.
Continuity mistake: After Cindy thanks the Grinch for saving her, he stops at the door. He slides his hand down the glass, and it comes off the glass well below his chin level. When he turns around, it's just at his chin height.
Continuity mistake: When Lou enters the classroom, the teacher's yardstick switches position from straight up and down to flat as the shot perspectives change.
Other mistake: When Lou and Cindy-Lou come home, Betty asks Cindy-Lou to unscrew the bulb in the refrigerator. A few moments later, Lou answers the phone, and repeats the question "Is my Sub-Zero Chillabrator running." Betty seems to have used an un-Who like term.
Visible crew/equipment: When the monster comes out of the Grinch's door in the beginning, the camera's shadow is visible at the bottom left corner. (00:05:12)
Answer: It was a rocket sleigh.