She is portrayed by Samantha Mathis.
Daisy was born after being hatched out of an egg, in the St. Theresa's Cathedral, after her mother was being pursued by King Koopa, an evil ruler of an alternative dystopian world.
She grew up and became an NYU student in paleontology digging for dinosaur bones under the Brooklyn Bridge. However, a mafia-operated business known as the Scapelli Construction Company threatens her and the dig site if the digging doesn't end sooner. This forced her to find a phone to call in the university for more security, to she encounters two Italian plumbers: Mario and Luigi, in which the latter found an instant attraction to her.
He tries to muster up the courage to ask her on a date with the help of his older brother Mario, which she agree, and they wound up on a double date with Mario's girlfriend Daniella. After the date, Daisy took Luigi back to the bridge to dig for bones, only to find two of Scapelli's men sabotaging, and leaving to water pipes open. Mario and Luigi manage to fix it, but were knocked unconscious by Iggy and Spike: Koopa's cousins and henchmen and kidnap Daisy, where they took her to an interdimensional portal to Dinohatten.
Koopa wanted a rock that Daisy had around her neck, which was a meteorite fragment, that would be used for Koopa to merge the two worlds together, but it was taken by the Mario Bros. when Luigi tried and fail to save Daisy. It is also revealed to Daisy that she is a princess of this dimension, after Koopa overthrew her father, and turned him into fungus, her mother happened to be the queen that send her to Brooklyn for safety. She was taken to the Koopa-Tower where she meets Yoshi. Koopa then revealed to her that she was descended from the dinosaurs, and believed she is the only one who can merge the two worlds together because of this heritage. With Yoshi's help, she manages to escape, after Lena: Koopa's girlfriend/assistant almost tried to kill her, out of jealousy.
She eventually was saved by the Mario Bros. with a little help from a Goomba named Toad, who was originally a guitarist that was turned into Goomba by a machine created by Koopa. Daisy and Luigi found Lena as, she was about to use the stone to merge the two worlds, to which doing so manage to overwhelmingly kill her, as she isn't destined to do so. The two worlds were beginning to merge: much to Koopa's delight, but Luigi and Daisy remove the stone causing too two worlds to be apart once more.
After Mario and Luigi defeated Koopa by using devolution guns and using bob-ombs to blast him with, causing him to turn partly into his Tyrannosaurus Rex form before devolving into primordial slime, everything was well as the citizens celebrated the Mario Bros. for their victory, and Daisy's father was turned back into his rightful form reclaiming his throne. When Luigi asked Daisy to return to Brooklyn with him and Mario, she claimed that she couldn't for she is a princess, and she has to set things right after all the damage that Koopa has done, and she wanted to spend more time with her father.
Three weeks have passed, and Daisy showed up surprisingly at the Mario Bros. apartment ask for help on a new mission to which they all agree too.