Role in the film
Alexander doesn't exactly have an easy life, as he always had bad days every day.
After waking up with gum in his hair, he gets an email about Phillip Parker's expensive birthday being on the same day as his. He told his family that he couldn't compete, but they didn't listen. On his way to school, a boy was seen photoshopping Alexander's face onto the bodies of women in photos, and then posted them online.
By the time he got to school, not only was he humiliated, but he learns that his best friend, Paul, was going to Phillip's party. He tries to ask his school crush, Becky Gibson, but she refused as well. Afterwards, Alexander accidentally burned down the periodic table with her notebook and got blamed for it. While waiting for a long time outside of school, Alexander was put in charge of Mel, the class guinea pig.
Later that night, Alexander tried to talk to Anthony about his bad luck. While Alexander thought that Anthony loved him as a brother, Anthony was actually talking to Celia on the phone. While Anthony was talking to Alexander, Celia, thinking that Anthony was trash-talking to her, abruptly hung up, and Alexander heard Anthony calling him an "idiot brother". At midnight, Alexander makes himself a birthday sundae and wishes that his family would see what it was like to have a "terrible, horrible, no good, very bad day".
The next day, he sees Emily having a cold, and then wakes up his parents, who were oversleeping. As Alexander leaves the bathroom, Anthony comes in, and reacts in horror when he looks in the mirror and sees a zit on his forehead.
At school, Alexander hears from Paul that Phillip's birthday party was cancelled, as he has the chicken pox, which meant that Alexander's party was back on ("His pox is your gain"). Becky even mentioned showing up. Alexander even hears that Becky's brother, Elliot Gibson, the boy who made the mean photoshops about him, had gotten suspended.
Throughout the day, while convincing them that their bad luck was his fault, Alexander learned that Trevor got green ink all over his face. Alexander and his family later see Anthony accidentally trashing their van, which resulted in him failing his driving test. Emily got drunk due to drinking too much cough syrup and ruined the Peter Pan play.
By the time the Coopers picked Celia up for the prom, he and most of his family were playing music into their fists with their mouths. At a Japanese restaurant, Alexander saw his father catching food into his mouth eight times in a row, and then accidentally set his sleeves on fire (which he put out using water from a lobster tank). While Ben walked out feeling disappointed (and trying to hide it), Alexander followed, along with the rest of the family. After realizing that they got to spend the worst day together, they began kicking trash cans around.
After getting home, they discovered a vicious lizard in the living room. In the backyard, Alexander discovers that his parents had rented an Australian petting zoo for his twelfth birthday. During the party, he learns that Paul and Becky have shown up. During the closing credits, they were seen pretending to surf.
- Alexander appears to be fond of Australia, as he has Australian stuff in his room. He was also seen eating a spread that was originally made there.