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Meet Zack and Cody, 11 year-old identical twins and the newest residents of Boston's swanky Tipton Hotel. Living in a suite with their mom Carey, the boys treat the Tipton like their own personal playground.
Cody is graduating from 8th grade as class valedictorian. But Zack is horrified to learn that he has to attend summer school and tries to hide it from his parents. Meanwhile, Maddie becomes a camp counselor at a run down facility with less than ideal girls under her wing.
Cody searches for a summer job, and finds a "help wanted" sign at the local mini-mart. When the owner realizes Cody is friends with London, he will only hire Cody if he will set him up on a date with her. Zack discovers he is the smartest student in his summer-school class, all the other kids make fun of him.
The tabloids report London doesn't know how to swim, so she takes swimming lessons. Zack has been offered to work at the hotel as a plumber or to work at a local market.
Zack and Cody wish for superhero powers when they see a shooting star. Their wish comes true and they learn that Mr. Moseby is their villain, who wants to turn all kids into miniature adults.
Zack gets a job at the minimart, but has to deal with Cody bossing him around. Meanwhile, London doesn't know how to present Lance to her friends.
A competing minimart issues a competition to see who can bag items faster, Zack and Cody accept the challenge. Meanwhile, Mr. Moseby's niece Nia is goofing off with London.
Zack and Cody rent out London's Suite while she is out of town so that Stacie, a cute girl from school can have a sleepover birthday party at the hotel.
When Zack and Cody invite Arwin over for dinner he won't seem to leave. Carey is getting annoyed at him so she forces Zack and Cody to make him go. Meanwhile, Lance dumps London and she wants to find a way to get back with him.
London (even though she can't sing or dance) gets the role of Sharpay in their school production of High School Musical instead of Maddie because Mr. Tipton is financing the director's play "Floss" on Broadway. Zack has to work backstage for detention and Cody gets the part of Troy.
It's the first day of high school for Zack and Cody. For the first time, London has to attend public school.
Zack tries to negotiate a better contract for Carey as the Tipton's nightly singer. Nia and London both want Cody's help with their science projects.
A monster-like robot is accidentally released into the hotel, due to the twins. A Halloween party is thrown by London. A typical prank.
Maddie is back and is not getting along with Nia, while Estaban is not getting along with Patrick, and the rest of staff aren't getting along either. So, Mr. Moseby hires a professional to help the team get along. Meanwhile, when Zack causes some customers to leave, he and Cody schedule a bug convention at the Tipton to make it up to Mr. Moseby. However, due to his fear of bugs, he accidentally releases the bugs into the Tipton.
Cody is currently with Barbara, but during orchestra class, Russian violinist Sergei joins as a guest student and starts flirting with Barbara. One of the classmates starts a rumor that Barbara and Sergei are moving back to Russia and are going to sell llamas, making Cody extremely jealous.
Zack and Cody each invite a girl over to their dad's empty apartment. Meanwhile, London teaches Esteban how to act rich because his family has seized power in his native country.
Cody helps London with her online video website. Meanwhile, Zack and Mr. Moseby become addicted to a certain video game.
Tony Hawk checks into the Tipton; Maddie and London has a crush on their fencing instructor. While Zack and Cody are doing their science project, the problem is that Cody has a fear of germs, and when Zack makes a mistake when analyzing a germ from the kitchen and thinks it's a toxic type of black mold, the rumor spreads through the hotel and everyone starts panicking. Cody gets over his fear after he realizes that he can't go skateboarding with Tony Hawk wearing an anti-germs suit.
Zack and Cody befriend Travis, a kid whom they rope into helping them impress their dates. They then bail on Travis and go out with their dates, but lets Travis go with the girls instead. Maddie finds a stranger's phone whom she thinks is her crush (because she and the stranger have many of the same interests, which she found out on the lost phone). At the end, the owner of the phone was an old man, but Maddie takes an interest in the old man's grandson.
Zack tries out for the high school basketball team but realizes there's some stiff competition, the kind he didn't face in middle school, and worse yet, the giant, in-your-face Coach Little (Michael Clarke Duncan). Meanwhile, when they're rejected as cheerleaders, Cody and London form their own cheerleading squad with the help of Mr. Moseby.
Maddie, Cody and Zack compete to get the best guest for London's online chat show. Luckily, The Cheetah Girls and Chris Brown are staying at the Tipton, but who will end up winning the competition?
