Danny Phantom (2004) : 2x15

Vlad's up to something and it involves Danny. After he sends three ghosts to Amity Park to battle Danny Phantom, it is revealed that he's working on his creepiest project yet: a clone of Danny Phantom. So far, the clones he creates can't sustain their forms for very long, but Vlad is determined to succeed. Danny doesn't have long to worry about Vlad's ghostly visitors, however, because he's distracted by the appearance of Danielle, a cousin he didn't know he had. And then, Danielle reveals that she too has ghost powers -- she's Dani Phantom! Unfortunately, she's also a product of Vlad's experiments, and therefore an imperfect ghost with an unstable form. Danny must convince his new "relative" to turn on her creator and help him destroy Vlad's evil experiment, before it's too late for both ghost kids.