Demigods are NOT supposed to use communication devices.

Annabeth is seen using a tablet to find a cure for Thalia's Tree.

The hunters are law enforcement officers and don't wear costumes.

The Stalkers wear crazy costumes and have fantastic nicknames.

Gary and his friends steal a car to go around the city, they get chase down by the police, but a dog gets in the way and they crash. Gary is the only one that got caught

Eggsy and his friends steal the car of one of Dean's henchman, because he kick them out of his bar. They get chase down, a dog gets in the way and Eggsy's friends escape as he's getting caught

It is Jed who looks after the Swede in the tent

It is Etienne, as Jed's character doesn't exist.

Ariel stays in one of the palace rooms after being brought to the castle.

Ariel explores the castle and examines various objects she sees. Eric meets her again and has a pleasant conversation with her about the things he collects from his voyages. Ariel crushes a piece of coral and reveals to Eric a beautiful stone that was hidden in it. He is impressed. They bond while he shows her various maps of his voyages. She tries to teach him how to blow a conch shell; he fails.

May Li never meets Helen Chao, and never goes to her apartment. Upon wakening up in Helen's bed, Wang Ta agrees to an affair, but eventually abandons her. Helen eventually gets her face treated by a doctor and regains her good looks, but she commits suicide after Wang Ta rejects her.

Mei Li comes over to Helen Chao's apartment to drop off Master Wang's coat for repair. She sees Wang Ta's jacket on the chair and leaves. Wang Ta wakes up late and insists he needs to leave even though Helen begs him to stay. He leaves anyway. Helen is not seen or mentioned again in the film.

Vee lives in Seattle.

She lives in Long Island.

In the book, Lily has blonde hair

In the movie, Lily has brown hair.

The tournament director treats Beth and her mom to dinner after her Kansas City win and tells them about Russian chess.

Matt and Mike go to dinner with and discuss international chess Beth and her mom after Beth wins in Kansas City. Mrs. Wheatley pays.

Dr. Wiezak, after hearing about Johnny vision of Stilson, thinks for a while before deciding that he would kill Hitler if he could travel back in time. First he is concerned about Johnny even asking the question.

He answers quickly and without much thought. He shows no concern for Johnny.