It's a fun idea that Barny Stinsen is also Billy Horrible are the same person, so here's a little bit of that as a cross over

...

It started as a normal day. It was still a couple months before their wedding, and Barney and Robin were shopping around for a baker for the wedding cake. Robin was looking at a pamphlet and Barney was pointing to one that he knew of word of mouth when he ran into someone.

"Oh, sorry about that!" A voice saif, catching Barney as he stumbled.

"That's fine, I wasn't watching where I was wahahah... " His voice trailed off when he realized who it was he ran into.

The person was rather tall and muscular. Someone he never in a million years he'd thought he'd see again. His mouth felt very dry.

"Are you ok Barney?" Robin asked. Barney couldn't answer he was in shock.

"You look HORRIBLY familiar. Do I know you?" The man in front of him asked.

Out of reflex he answered. "No, one of those faces I guess."

Recognition filled Captain Hammer's face. "It IS. You, isn't it, Doctor?"

Barney pulled a face, "Doctor? Please. Who has time for that?"

"I know it's you, Doctor Horrible. So this is where you've gone off to after all these years?"

Barney's heart was pounding. Of all the things he'd thought of when planning his wedding, it was someone like THIS asshole showing up months before his wedding. Tho he almost didn't recognize Captain Hammer without his signature gloves.

"I'm sorry, I honestly can say that I don't know what you're talking about." Barney said, stepping back from the other man. Tho when he last saw the corporate tool he had lost his powers, he was still much bigger than him and stronger. All he did was lose his invulnerability.

"Barney, what's going on?" Robin was clueless to the exchange, and Barney's behavior was concerning.

"Nothing Robin, this man is obviously confused. " Barney tried to lead Robin away, but his arm was grabbed by the other man's hand. Yep, he still had superhuman strength.

"Who is THIS lovely young woman? Did you finally decide to replace poor sweet Penny?"

Now Barney was starting to get angry. His heart pounding, with a slight twinge. He pulled his arm from the hero's grip, thankfully his grip wasn't as firm as it usually was and it didn't dislocate the shoulder. Again. But if this "hero" thinks he can steal someone else from him, he had another thing coming.

"Look, you obviously have me confused with someone else. My name is Barney Stinsen, not Dr Horrible. I don't even have a PhD, tho it would be AWESOME to have a doctorate in magic. I'm just trying to plan my wedding with my fiance. So if you could please, just leave us alone thank you." Barney glared at the man, just done with today.

" Very well." Captain Hammer said with a shrug. "But we will see each other again, Doctor." And walked off.

Barney watched as the man walked off, his blood pressure still amped up.

"Are you ok, Barney? You seem kind of shook up?" Robin slipped her hand around his arm, snapping him out od his thoughts.

" Yeah. I'm...fine. let's just head home, we can pick out a baker tomorrow."

...

Barney was still fuming when they got back to the condo. He almost lost it out there, what was Hammer even doing here in NY?

"Barney? What was that all about? Who is Dr Horrible?" Robin asked, placing her purse on the table. Barney had been silent the entire trip home, not even greeting Ranjit when he picked them up.

"It's nothing. I have no idea what that...guy was talking about." Barney said, swallowing the word he really wanted to use.

Robin approached him, arms crossed. "You know your a terrible liar when your face does that twitch. When did you even pick up a twitch?"

Barney rubbed at the right side of his face, trying to get his eye to stop blinking. It took a long time to break that habit. He sighed looking at the love of his life.

"It's...nothing. Dr Horrible is a thing of the past, and doesn't exist anymore."

" But who IS he? This whole incident has me curious."

Barney shook his head. " You're better off not knowing. SAFER not knowing"

Robin realized tho she knew alot about Barney, and was still learning his past. He obviously still had secrets held in his heart. Tho secrets were ok to have, this one obviously weighed heavy on him. "But it's obviously hard for you. Whoever that guy was, he's from your past and knew exactly how to try to hurt you." That was the understatement of the year. "Barney... Who is Penny?"

At the mention of that name, he recoiled. Even tho it was so long ago, the regret felt fresh. He clenched his teeth and shook his head. "Someone who died a long time ago, around the same time Dr Horrible disappeared"

" I see." Robin thought she knew all about Barney's exploits, but never once had he mentioned a Penny. She was obviously more than that given his reaction to the name. "So who was that guy? He seemed to have a personal grudge with you."

Barney rolled his eyes. "Captain Hammer, corporate tool. He likes to think himself a hero but he's not."

That was all he said about him. He still seemed closed off on the whole thing.

"Barney, I love you. If you think this Dr Horrible thing would change that, your wrong. Even tho it sounds like a villain name, if Captain Hammer is a hero."

Barney sighed. " It IS a villain name. Look. It's from my past, and it's not something I'm proud of, well I'm proud of some things, just not all."

He grabbed a notepad off the table. And wrote a website and login info on it. " Here, you'll find all you have to know about Dr Horrible on this site. But promise me you won't show this to the other. Like I said, the less people know about Dr Horrible the better."

...

Robin went to her laptop later that evening while Barney was in the shower and visited a website that hadn't been accessed in years. There she saw blog entries from a evil scientist by the name of Dr Horrible. It was endearing almost, seeing her soon to be husband talking about changing the world, anarchy and social change. She knew Barney was smart, but this was new. When she saw the final entry, she realized why he said it was dangerous for people to know. Dr Horrible wore a read leather lab coat and glasses over his eyes. And had a different air to the previous entries. After watching the video she turned off the computer and looked up to see Barney standing at the bedroom door in his suitjamas.

"So?" He asked, arms crossed and seeming alot more vulnerable than she's ever seen him.

"It was enlightening. But if you think any of that would change how I feel about you, it doesn't. I can actually agree with alot of your ideals." She walked over to him and looped her arms over his head to give him a kiss.

"Really?" He was almost in shock. "You don't think any less of what I've done in the past?"

"Barney, the past is in the past. You're very different than what I saw in some of those videos, yet in a way you still have some of those aspects."

" I do?" He thought for sure all parts of that person were gone over the years.

"Yes you do, Doctor." She said seductively.

Barney chuckled, he didn't think he could love Robin more than he did, but every day she surprised him.