Generic 'switch everyone's gender' genderbending is boring. Have an AU where ghost forms are synonymous with magical girls.
Not So Weird
Danni Phantom flew into her friend's bedroom window. She was grounded again thanks to having to ditch math class to deal with the Box Ghost and she needed the notes for the test tomorrow. Although they should be used to it by now, she still felt their stares as she adjusted her gloves, smoothed her ribbons, fluffed her very short skirt, and tugged her stockings back up to her thighs. She still didn't know why she had to wear this when she transformed but at least now she knew she wasn't the only one.
The transformation rings flashed and pulled away, revealing his normal t-shirt, baggy blue jeans, and floppy black hair. Not a ribbon or bow in sight, no ruffles, not even curves. "C'mon, guys, this can't be weird forever," Danny pleaded. "So my ghost looks like a magical girl. That doesn't necessarily say anything about me."
"I dunno, man," Tucker said. "You were never into girly stuff before. Now you, like, brush your hair."
"It's called 'grooming', Tucker," Sam scoffed. Still, she'd been staring as much as he did, she merely tried to hide it better. No reason to make Danny feel more uncomfortable than he was already.
"Well, I'm not the only one like this, so..." Danny said, crossing his arms over his chest.
Two sets of eyes turned on him. "Wait, what?" Tucker demanded. "There's another?" Sam asked. "Who?" "Who?"
Danny held up his hands. "Before I say anything I need you both to promise me," he said. "Promise me that this isn't going to leave this room. That the three of us are the only ones who are ever going to know. He knows my secret too and I kinda forced him into a truce by saying it was going to stay secret. You can't tell anyone. Got it?"
"Depends on who it is," Tucker said.
"Tucker! This is serious! He knows about me! He knows Mom and Dad. If this gets out about him I go down just as hard. How many people out there are going to want to capture a magical girl? We don't know! If you're gonna risk that, I'm not gonna tell you. And then I'll have to deal with my new archenemy all by myself. Do you really want that?"
"Whoa, chill," Tucker said. "I'm kidding, I'm kidding. Look, we're not gonna tell anyone. At worst we're gonna laugh at him."
Sam nodded in agreement and Danny felt odd, like there was something wrong with that somehow. He sighed. "Vlad Masters," he admitted.
Tucker burst out laughing.
Danny glared. "Tucker, I'm going ghost," he warned before she pointed at his hat and very carefully shot it off. Tucker squealed before grabbing his hat and making a fuss about the burnt spot.
"This is the same Vlad Masters who won't date and has been trying to buy the Packers, right?" Sam asked.
Danni nodded.
"So he is compensating for something," she mused. "It's common knowledge. People just think he's gay, though. Wait, so Vlad Masters..."
"Turns into a really hot woman in a tiny white dress slit way up to here," Danni said, pointing to far up on her hip. "Blue skin, Disney-villain hair, a big white and red cape, and the creepiest 20-year long crush on my mom. And she was the most powerful bad guy, living or dead or otherwise, that I have ever faced. She wiped the floor with me while complimenting my panties and giving the whole evil 'join me and I'll train you as my apprentice' speech."
"Wow, so he's actually..." Sam realized.
"Dude, you're screwed," Tucker said.
"Tell me about it," Danni pouted. Her eyes fell on her purpose for coming today. "And now I'm gonna fail math, too! How am I supposed to study now?"