Nightmerica is a female ghost, parody of the Freddy Krueger character from the A Nightmare on Elm Street franchise. Originally just a movie character inside the Danny Phantom world, Nightmerica came to life as a ghost when Desiree overheard Sam saying "I wish something really bad happens to Paulina."
When Danny and Tucker decide to go to Paulina's Quiceañeras' party instead of going to the movies with Sam as they promised, she wishes for something bad to happen to her. That's when Desiree overhears Sam and brings her along with the other two characters to life in order to kill Paulina.
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