Thanks to everyone who reviewed and answered my question. I'm making Jazz know right off the bat. Hope you all enjoy! I don't own Danny Phantom.

This was too much; Danny just wanted to grab the mirror and break it into millions of pieces. He reached up and punched the mirror, but something very strange happened. Instead of his hand hitting glass, it went right through it. "No way," Danny said in awe. Danny closed his eyes, trying to get a grip on what was going on; when his eyes opened again, he saw that he was gone! "Oh no! What's happening to me? Where am I?" Danny was starting to reappear in front of his own eyes in the mirror. "Something is definitely wrong," Danny concluded. Just as soon as the shock had worn off, footsteps could be heard coming down the stairs.
"Danny, you here?" It was Jazz.
"Oh no! I can't let Jazz see me like this," Danny thought. "Come on! I've got to disappear again." He started to think hard, trying to make all of this weirdness actually make sense. Jazz's footsteps got louder and Danny wasn't getting any clearer. He ran inside the ghost portal and hid into the very back of the machine.
"Come on Danny, I know you're up here. Mom and dad said so." Jazz started looking around and ended up at the ghost portal. She stepped inside while Danny stepped back. "Huh? I know he's in here!" Jazz thought to herself. She started to lean against the switch that had caused Danny a world of trouble.
"JAZZ, NOOOOO!" Danny yelled as he ran to grab a hold of Jazz. As soon as he grabbed her arm, both of them phased through the wall of the portal. Both of them reappeared on the ground, with Jazz staring at Danny. He started getting up; feeling very scared and embarrassed at what had just happened.
"D-Danny? Is that you?" Danny started to open his mouth, in which Jazz flinched at the sight.
"Don't be afraid Jazz," Danny said, sounding sincere. "I promise I won't hurt you."
"I-I have to go." Jazz said feeling frightened. She got up and headed for the stairs. Without warning, Jazz suddenly yelled, "MOM! Da-" Danny ran up and sealed her mouth before Jazz could finish.
"Jazz, please! You can't tell mom and dad. Please? I mean, I don't even know who I am or what happened."
"But Danny, they have to know," said Jazz, taking a step towards the stairs. Danny was too quick for her and in a blink of an eye, he had managed to phase through her.
"Jazz? What is it that you want honey?" called Maddie from upstairs.
"Jazz please? I promise I'll explain what I can to you once I find out. Please, I'm asking you as your brother? Please?" Jazz stood frozen for a minute, contemplating the situation.
"Nothing mom," she finally concluded.
"Phew! Thanks Jazz," Danny said gratefully as he was trying to hug Jazz; but instead, he fell right through her.
"No…problem," Jazz responded. "So, what exactly can you do Danny?"
"Well, so far all I can do is faze through stuff and go invisible."
"And you can fly," Jazz added.
"And I can…FLY?!" Danny looked down at his feet and realized that he was floating up above the ground. "Great, just more of what I don't want," Danny said remorsefully.
"Can you change back?" Jazz asked.
"That's just it," Danny began, "I don't know what I can do with these…powers, and even if I'll be the same again or even change back to my old self."
"Well, how'd you end up like this in the first place?" Jazz asked, looking Danny up and down carefully.
"You wouldn't believe me even if I told you."
"Try me."
"Well, it was from mom and dad's stupid Ghost Portal."
"You're kidding?!" Jazz asked starting to laugh.
"It's not funny Jazz!" Danny angrily shot back.
"One of their inventions actually worked?!" Jazz's expressions of laughter and amazement soon turned to fear. "You're not going to tell them, are you?" Jazz asked as she grabbed Danny by his jump suit.
"Of course not--," Danny began.
"Good, because if mom and dad found out that one of their stupid ghost inventions actually worked, well, who knows what could happen?" Jazz said worriedly.
"Gee Jazz, nice to know you really care about me and not yourself." Danny said annoyed by his sister's comment.
"DANNY! JAZZ! YOU TWO STILL UP THERE?!" Maddie's voice called from up the stairs.
"Oh no! Mom and dad!" Jazz and Danny both said in unison.
"Jazz, you stall mom and dad as long as you can, and I'll worry about changing back, if I can."
"All right. But I can only stall them for so long, so you'd better learn how to change back fast. And Danny?"
"Yeah Jazz?"
"Remember…don't tell mom and dad about their Ghost Portal working. With any luck, this could deter them from wanting to do anything more with ghosts."
"Right, can do Jazz." Danny said, giving Jazz a salute while rolling his eyes. Jazz left the lab, leaving Danny alone to figure out how to change back with no time to spare.