Holly O'Neil is a young girl who first appeared in the The Suite Life of Zack & Cody episode "Have a Nice Trip" as a character who cheated people, pretending to be bad at something until they competed with her.

She struck a bet with Zack MartinMaddie Fitzpatrick, and possibly other people that she would win at a game, and since they believed her to be a bad player, they agreed to the bet. She is known to sell fake cookies to people, and her father faked an injury to receive special treatment. She is probably about six or eight years old.

A while later, she is found attending "Camp Heaven on Earth," with Maddie as a counselor. In one episode, she sold London Tipton's secrets with the rest of the cabin, having heard Maddie talking to London on the phone.