A/N: So, this is a crossover AU of Danny Phantom and MegaMan Battle Network. MMBN characters won't make an appearance, though, so you probably don't need to know much about MMBN to understand it. Basically, all ghosts are AIs called NetNavis, except for the animal-like or otherwise non-sentient ones, which are viruses.

Anyway, enjoy.

As he watched his friends carry his unconscious body up to his bedroom, Danny realized exactly how stupid of an idea it was to test out his parents' unfinished inventions. In retrospect, he really should have seen this coming, but it seemed like a good idea at the time.

Initially, Danny was only planning on showing Sam and Tucker around his parents' lab. Being experts in virus research, they naturally had a lot of cool stuff in there. The place had wall-to-wall monitors connected to powerful computers, many of which were entirely dedicated to virus containment and observation.

There was one particular machine they wanted to see: the helmet that put your consciousness in the Net, allowing you to directly interact with viruses and NetNavis alike. His parents called it the Net Portal. He had always been curious about it, but since it didn't work quite right, he never had the courage to try it out.

"So, it doesn't actually take you into the Net?" Tucker asked, holding the helmet up to his face to get a better look.

"No, it does," Danny clarified. "I see them do it all the time. Apparently some other function isn't working right. They've been trying to figure out how to manually NetBattle instead of relying on Navis to do it for them." Danny's PET buzzed in his pocket. That usually meant his NetNavi, Phantom, had something to say, so he took it out and flipped it open.

"Also, they could be back any minute, so we should probably make this quick," Phantom said.

"If it works, then what are you waiting for?" Sam said as she snatched the helmet out of Tucker's grip and handed it to Danny. "You can visit the Net in person! Aren't you curious? You gotta check it out!"

"Yeah, that does sound cool," Danny admitted.

"And I'd finally get to meet you face to face," Phantom added.

Danny was also looking forward that, having only ever seen Phantom through a digital screen. That thought alone was enough for Danny to make up his mind.

He jacked his PET into the helmet and put it on.

"Well, here goes nothing," he said as he started up the machine. In an instant, Danny's view switched from looking at his friends directly in front of him to looking at them through a camera. He watched his body go limp as Sam and Tucker rushed to catch him and sit him down on a nearby chair.

"Woah! You okay, Danny?" Sam asked Danny's unconscious body.

"Yeah, I'm fine," Danny replied, hoping they could hear him. Luckily, it seemed that the helmet was connected to one of the lab's many computers, because they immediately turned to face him.

"Well, that could have gone a lot worse," he heard Phantom say. Danny looked over his shoulder to find Phantom standing next to him with his arms crossed.

Seeing him in person felt different from seeing him through the screen of his PET. He could see Phantom in a lot better detail. Neither his black jumpsuit nor his white gloves and boots looked like any sort of material Danny had ever seen before, but he supposed that was only natural, considering all of it was digital. As usual, Danny couldn't see anything past the visor of Phantom's black and white helmet, except for the glow of his bright green eyes. Danny had never seen Phantom's face without it, so he wasn't sure if the visor could even be removed at all.

"Man, that is so cool," Tucker said, snapping Danny back to reality. "What's it like?"

"I dunno. I don't feel that different," Danny said. He looked down at himself and was surprised to find that he looked sort of transparent, like a hologram. He didn't look very solid, so he wondered if he was able to touch anything. He reached out to touch Phantom's arm.

The world shifted around him. Suddenly, he found himself alone, staring at Sam and Tucker's shocked faces.

"What happened? Where'd Danny go?" Tucker asked.

"I'm right here," he said. Was he missing something? He should have shown up on the screen, since he was pretty sure he hadn't turned invisible.

"Phantom, this isn't the time for joking around! Where is Danny?" Sam demanded.

"I'm not joking around, I'm-" he started, but then he realized that something was off. He held a hand in front of his face and was only half surprised to find he was wearing white gloves. "Huh. I... think we might have fused?"

"Wait… So you're…?" Tucker said, putting the pieces together.

"I'm Danny and Phantom," he said. Strangely enough, even though both names were his, neither one felt quite right anymore. Danny Phantom, perhaps? He wished there was a better way to use both of his names at once, but it would have to do.

"Can you unfuse?" Sam asked.

"I'll try," Phantom said, though he hadn't the slightest idea how. He wasn't even sure how it happened in the first place.

He tried imagining himself unfusing, but that didn't do anything. It only left him unsettled at how much concentration it took to remember what it was like being two separate people, despite the fact that he had been two people up until a couple minutes ago. Then, he tried willing himself to unfuse, but he could only repeat unfuse, unfuse, unfuse in his head for so long before he got tired of it and gave up. He'd have to think of something else.

"No luck. Can you guys take a closer look at the helmet? Maybe there's some button on there that could fix this," Phantom suggested.

Sam and Tucker grabbed the helmet to inspect it, turning it around as Danny's limp body flopped around along with it.

"I found something!" Sam announced. "There's this switch labelled 'Synchro,' and it's switched on right now."

"'Synchro' as in 'Full Synchro' as in 'the minds of Navi and operator become one'? Yeah, that sounds like it would do it," Tucker agreed. "Try switching it off, Sam."

There was a click followed by silence as all three of them waited expectantly.

"Uh-oh," Sam said a moment later. "I think I hear your parents' car in the driveway."

"Quick! Jack me out!" Phantom said, panicked.

Sam unplugged the PET from the helmet, turned the helmet off, and took it off Danny's head, but didn't know what to do when his body remained unresponsive.

"I may not have fully thought this through," Phantom said from inside the PET. "Look, just carry me to my room, we'll figure it out from there."

Tucker grabbed Danny's torso, and Sam followed his lead, attempting to carry Danny's legs and his PET at the same time. They made it out of the lab and almost all the way to Danny's bedroom when Danny's parents opened the front door.

"Hi Mr. and Mrs. Fenton, Danny's asleep so we're carrying him to his room, nothing's wrong, later!" Sam said hurriedly as she and Tucker put Danny on his bed and closed the door.

It took at least half an hour for them to get Danny's body up and moving again. Sam and Tucker's initial relief switched back to worry when Danny winced and put his hand to his forehead, but Phantom was the one that said "Ow, killer headache."

Danny spent a lot of time looking at himself through the PET. Phantom didn't have the visor down for the first time ever, and his face didn't look anything like he would expect. Aside from the glowing green eyes and the white bangs poking out from under his helmet, he looked just like Danny.

He couldn't be sure, but as far as he could tell, his human body and his Navi body were blinking in unison.

"This is really weird," both of him said at once. Well, having his real body regain consciousness was sort of an improvement. The biggest problem was getting the hang of controlling two bodies at once. So far, he had little control over which mouth he was speaking from.

"Yeah, because everything was completely normal before you finally started moving again," Sam said sarcastically.

"So, this is weird to you, but being a Navi wasn't?" Tucker asked.

"Not 'wasn't,'" Danny corrected, "'isn't.'"

Sam and Tucker looked at him like he had suddenly started talking backwards.

"I'm still fused, or in 'Full Synchro,' or whatever it's called," Danny explained. "Being able to control both bodies again doesn't change the fact that I'm still one person."

"Man, you're right," Tucker said. "This is really weird. Are you gonna stay like this? What do we even call you now, Danny or Phantom?"

"I've been considering 'Danny Phantom,'" Phantom said.

"Are you sure we shouldn't tell you parents about this?" Tucker asked. "They are experts at this sort of stuff."

"I- I don't know," Danny said. "I'm sort of… conflicted about it, I guess."

"What do you mean?" Sam asked.

"Well, Danny probably would have wanted to tell my parents about it right away, but Phantom wouldn't have told them unless it was absolutely necessary." Phantom said.

"So I have one part of me that trusts that they'd solve the issue, and another part of me that's afraid of what they'd do with me afterwards." Danny continued.

"Oh," Sam realized, "you mean because of…"

"Yeah," Danny said. He'd told her and Tucker the story of how Danny and Phantom met, so they understood why his parents would make him uncomfortable.

"Don't worry, Danny," Tucker said, putting his arm around Danny's shoulder. "We won't tell nobody if you don't want us to."

"Yeah," Sam agreed, "it'll be our secret."

"Thanks, guys," Danny said, relieved.

A/N: Technically speaking, this isn't exactly how Full Synchro is supposed to work, but there's, like, three different canons for how Full Synchro works, so whatever. Actually, it's pretty close to the manga version of Full Synchro, with a few exceptions.

Anyway, I'm not sure how long this is going to be, but I do have at least one more chapter in the works.