
Sam can barely contain her contempt for the "Miss Teenage Happy Princess" beauty pageant and its organizer, Dora Mattingly, when they descend on Casper High. She decides to enter the contest to make a statement about individuality, but makes a discovery instead: Dora Mattingly is the Dragon Ghost! Before she can get to the bottom of the mystery, she's inadvertently crowned Miss Teenage Happy Princess by its happy-go-lucky judge... Danny Fenton! When the tiara is placed on Sam's head, it magically transports her to a castle in the Ghost Zone, where she learns she's to be the bride of Dora's brother, the ghostly Prince Aragon. As Danny and Tucker head into the Ghost Zone to rescue Sam, she does her best to shake things up in the medieval ghost world she's stuck in.
Danny and Sam get into a fight, and when Sam utters the words, "I sometimes wish I'd never met you," she finds herself in a world in which she and Danny are strangers. Worse than that, since it was Sam who encouraged Danny to check out the Fenton Portal the night he got his ghost powers, Danny doesn't have any powers! Now, Sam must convince Danny that they share a friendship and a history, and lead him back to the Fenton Portal for a second "accident" so he can again become Danny Phantom.
After being bitten by tiny green ghost beetles, the kids of Casper High get a mysterious illness that gives them ghost powers and are quarantined at a spooky old hospital outside of town. When Danny sneaks into the hospital to investigate, he is captured by Penelope Spectra and her assistant, Bertrand. They are the ones who started this illness as part of their plan to build Penelope a young and beautiful new body. All she needs is Danny's half-human/half-ghost DNA to complete her ghostly plan. With Danny captured and Sam sick, it's up to Tucker to conquer his fear of hospitals and free Danny before Penelope gets what she's after.