Danny Phantom centers on the life and adventures of 14-year-old Danny Fenton, an unpopular but good-natured boy attending Casper High School in his small American hometown of Amity Park. He lives with his eccentric ghost hunting parents, Maddie and Jack, and an overbearing 16-year-old sister, Jazz (short for Jasmine). Upon pressure from his best friends, Sam and Tucker, he decides to explore his parent's Ghost Portal. They had created it with the intent of finally bridging the real world and the Ghost Zone (the ghostly parallel universe of Earth), but upon plugging it in, it failed to work.
Once inside, he accidentally presses the "On" button, (something that his naive parents failed to do), subsequently activates the portal, and due to him being inside it at that moment, it infuses his DNA with ectoplasm, transforming him into a half ghost boy, nicknamed "The Halfa" by the rest of the ghost community.
Danny, who calls himself 'Danny Phantom' in ghost form, develops the ability to fly, become invisible, and turn his body intangible at first and throughout the timespan of the series learns other powers such as his ghost ray, ghostly wail, and Cryokinesis. Danny panics over his newfound powers and initially has little control over them, but he soon realizes that he can use his powers to protect his town from ill-meaning ghosts.