Continuity mistake: After the Grinch stole all of the presents, Officer Wholihan gets into his police car and drags the mayor's bed out of his house. When the bed smashes through the window it breaks the top off the middle post of the bed. Then when it comes back to the shot of the bed it's been fixed.
Continuity mistake: When the Grinch is messing up the mail in the back room, he takes out a package and puts it in another one. When he takes his hand out the package falls out and lands next to the pile of presents. The mistake is when the camera goes to another shot, the package is not lying on the ground as it was before.
Continuity mistake: When Miss Martha May is shooting the lights onto her house you see them lit as they are being fed into and coming out of the machine when the camera is pointing on her but when it's a far off shoot only the lights coming out are lit not the ones on the feeding wheel.
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.