He'll be coming back along with his master in the movie remake (18 years since the Jim Carrey film), however it will be computer animated than live action.
It is unknown how or when The Grinch got him, but he presumably found him during his childhood.
He was first seen when he scared the Whos with the huge monster with a growl. His master, The Grinch, was proud of him for scaring them, but upset that the Whos won't leave him alone.
The Grinch came up with a plan to prank the Whos at Whoville. Their plan works until they met Cindy Lou Who at the post office, and when Cindy's in trouble, Max order his master to save her, which The Grinch did.
After saving Cindy, they left and made prank calls until they decided to go home to Mt. Crumpit.
He wasn't seen again until Cindy came to Mt. Crumpit to invite his master to join the party, and later on, The Grinch decided to go.
When The Grinch was having a bad time (thank to the mayor), he came home and realized that Max was having a party by himself and having a great time.
Then, his master threw him out and told Max that if he's not gonna help, he'll do something bad to him until somehow Max gives him a idea: to dress as Santa Claus, so he can steal Christmas.
Before they head to Whoville, The Grinch realizes that he forgot the reindeer and notices that if he can't find one, he'll use Max instead.
His master makes Max into a reindeer and they head to Whoville to steal presents from every single house. After they got every single present, they headed home, but the sled ran out of gas.
The Grinch made Max pull the sled all the way home, and Max was tired after they both got home.
While his master was about to push the sled, he and Max realize that the Whos are singing without any presents. At first, The Grinch was mad about it, then confused and suddenly realized that Christmas isn't about presents, it's about spending time with the people you love.
After The Grinch realized what he had done, he told Max that he loves him, and Max gives him a happy lick until his master told him to give him some space. Then, Max realized that the sled is about to fall and warns his master.
After his master saved the sled and Cindy Lou Who, they head back to Whoville to bring the presents back.
At the end, we see Max was sitting next to Cindy as she serves him a feast and eating.
- Max, the male dog, is played by Kelley, a female dog.
- Max was originally going to be a CGI dog.
- Max appears to understand the English language by being able to obey specific commands by the Grinch, like what size wrench to bring him.
- Despite living with the Grinch, Max has a lot of Christmas spirit. Max is shown secretly dancing to Christmas music while the Grinch is away.