"They don't even know I'm here. They don't even know I'm here.'"
―Max, after realizing he's been left home by himself[src]
Max Mercer is a boy who was left at home while his family went to Japan.
Max and his family moved from London to Chicago two months before Christmas. They then planned to spend Christmas with their family in Tokyo. Prior to this trip, Much of his extended family was staying in the Mercer house, which upset Max. One day, on their way home, Max and his mother had to stop at an open house in order for Max to use the bathroom. At the open house, he spotted a doll the owners had, one his mother recognized as a very valuable doll.
Later, Max chafed as his uncles and cousins swarmed the house. To escape the noise, Max went out to the garage and started watching cartoons in a car.
The next day, as the family members who hadn't taken the first flight to Tokyo rushed around to get all their luggage into the cars, Max slept on. When he woke up, he went back inside the house to find that everyone was gone. Initially, he enjoyed it and spent the day playing and reading his sister's diary, but later in the day, he was scared when he heard Jeff and Pam McKenzie coming into his house. He heard them talking about retrieving an "ugly little boy" and selling him to an old lady. He tried to call the police with the Homebot, but it was still on German from when one of his cousins had changed it as a prank. Despite this, police came as Pam and Jeff had put in the wrong alarm code. Max watched through the window, but was shocked to see them not get arrested. He then imagined him telling the police officer, Buzz McCallister, he was home alone and his mother getting put in jail for leaving him alone.
That night, Max went to bed alone. He talked to the Homebot, telling it he missed his mom and asking it what to do. Homebot wasn't able to help, so Max went to sleep.
The next day, Max rode his bike to a church that was having Christmas Eve service. He looked fondly at the nativity before going inside, where they were collecting toys for a toy drive. Chris McKenzie came to bring a donated toy while Max was looking and they talked about their respective family issues. Chris then took the toy he'd just donated and gave it to Max, saying he needed it as much as anyone. Max then spoke to the lady who was collecting the toys and unwittingly gave the impression that his parents had died.
Max returned home to Jeff and Pam trying to break into his house again. He overheard them making a plan to return at night with Jeff in a Santa suit to trick him and made a plan to set booby traps around the house to keep them from kidnapping him. When they arrived, he watched as they fell into his traps. When they finally got into the house, Max fired billiard balls at Jeff, knocking him out. When Jeff woke up, he and Pam tried to reason with Max, saying they just wanted to talk. Max finally confronted them and said he knew what their plan was and they were shocked that he thought they were planning to kidnap him. They told him they really just wanted their doll back. When they learned Max was home alone, they said he could stay with them until his mom got back and took him back to their house.
The next morning, the McKenzies learned that their nephew, Ollie, had actually taken the doll they thought Max had. Max helped them keep the doll from getting broken when Ollie threw it. Then his mom came to pick him up. She took him back to the house, where she said they'd have Christmas just the two of them, and was shocked at the huge mess.
A year later, Max's family spent Christmas with the McKenzies.
Max is shown to be very creative, demonstrated when he builds a Lego bridge out of hundreds, if not thousands, of Lego bricks and builds an extremely intricate hot wheels track down his stairs. He's not afraid to harm others to protect himself as shown when he use icicles to slow down Jeff and use bullets with pins to shoot Pam in various parts of her body. He is also shown to be more aggressive than Kevin, as shown when he shoots Jeff right in the forehead with a pool ball. He also likes drinking sodas, as shown when he asks Jeff if he can have a pop can. He is also shown to like old cartoons, as shown when he turns on Looney toons when he gets in the car. He seems to be accepting at times, as shown when he tries to look at what his parents are doing on their computer but is blocked by a password screen and is fine with it.
- He's kind of like Kevin McCallister.
- Buzz mistakenly believed that Max's call about being left home alone was a prank by Kevin McCallister.