
Although Danny Phantom can perform extraordinary physical feats, Danny Fenton is still something of a weakling. For this reason, Dash is assigned as Danny's "fitness buddy" to help him prepare for the Presidential Fitness Test at school. When Skulker appears at FentonWorks on his usual hunt, Danny Phantom, Dash, and Skulker are accidentally hit with Jack's new "Fenton Crammer," which shrinks them all to a half-inch tall! Worse yet, Danny's ghost powers don't work so well in his tiny form. Now, Danny and Dash must rely on each other's brains and natural physical abilities to get to the FentonWorks Emergency Op-Center and reverse the shrink ray before Skulker and his brand new fully-powered ecto-skeleton catches up to them.
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.