Once Celestia had calmed down and Twilight had her fill of driving her crazy for the moment (which wasn't until they'd returned to the Ponyville library), Twilight gave the full story of what happened in the other world. Celestia...was not entirely approving, but Twilight could care less given she ran a successful universe in all but name. It was in the midst of the story that a nearby closet flared to light, and Nefarious stumbled out in his pony form. "Safe!" he called out happily.
"I think some introductions are in order," Twilight spoke up as she walked up to his side. "Nefarious, these are my friends of Equestria - Fluttershy-"
"Miss Disney," Nefarious concluded, making Fluttershy blink in shock.
"-Rainbow Dash-"
"Not much imagination on name, there," Nefarious jibed playfully.
"-Rarity-"
"Miss trying too hard," Nefarious teased, making Rarity lift her nose with an offended 'Hmph!'
"-Pinkie Pie-"
"The one that makes us look almost sane," Nefarious whispered as he hid behind Twilight.
"-and Applejack-"
"Can I drink her?" Nefarious asked eagerly.
"Say wut?" Applejack demanded, her eyes wide as she backed away slowly.
"Nefarious, behave!" Twilight snapped, smacking him in the back of his dome with a wing. She then continued her introductions. "This is Princess Celestia-"
"The one the bad guys try to kidnap to fight heroes, only to meet plumbers?" Nefarious quipped. "I read that message between you and Lawrence, you know."
"...I feel like I'm missing something," Celestia observed mildly. "Though at this point, I think I'm used to it." She reached for her tea.
"-Princess Luna-" Twilight continued, ignoring Nefarious' jibe.
"The awesome sister," Nefarious stated firmly.
"...my...thanks?" Luna offered nervously as Celestia pouted.
"-my old foal-sitter and sister-in-law, Princess Cadence-"
"Miss even-more-Disney," Nefarious interpreted. Cadence only giggled in response.
"-my BBBFF, Shining Armor-"
"Wow, not even trying to be subtle there," Nefarious observed.
"I...don't know how to respond to that," Shining observed, blinking.
"-and Spike."
"Mr. Underleveled," Nefarious concluded.
"I'm half Twilight's age, what's your excuse?" Spike countered quickly.
"Ooh, snarky!" Nefarious purred. "I like him!"
Twilight sighed, rolling her eyes. "Everyone, this is my boyfriend, Dr. Nefarious."
While most listening plainly weren't certain how to react, Rainbow Dash burst into laughter. "What'sa matter, Twi? Couldn't find yourself a boyfriend so you built one?"
"Hey!" Nefarious snapped angrily. "Twilight did not build me! My robotic form is the result of my genius in discovering a way to completely convert the biological to the robotic without neurological degredation or rejection!"
Luna's eyes widened in response. This seemed quite...intriguing.
"Yeah!" Twilight added. "The only part of him I built was his penis!"
Celestia promptly spat her tea all over Rarity's fainting couch. Rarity decided to faint dramatically another time, especially since Fluttershy had fainted for real.
"Twilight!" Nefarious grumbled. "Do you have to keep bringing that up?"
"What?" Twilight complained. "I thought you'd be proud of what a good job I did on yours. I mean, it's not every stallion whose pride can change shape and vibrate for added stimulation-"
"Woof," Cadence muttered under her breath, fanning herself as Rarity decided to faint dramatically on one of Twilight's couches. Noticing Shining's ears go flat, Cadence chuckled. "Now Shiny, dear, you know you don't need to be jealous."
"It's more I'm not sure I like someone who just screams 'I am a villain' in all but vocals dating my little sister," Shining grumbled.
"I AM A VILLAIN!" Nefarious screamed at the top of his cybernetic lungs, making Twilight facehoof. "Does that help, Knight boy?"
Shining snorted angrily. "Now listen here, I may not know everything about what she's been through, but she's still my sister! If you hurt her-"
"Clank's going to take whatever's left of me when she's through and rip it to pieces in the time vortex of the Great Clock to maximize how much he's able to make me suffer before my very essence degrades from excessive quantum strain," Nefarious interrupted. "Go ahead. Try and trump that intimidation."
"Uh...I...er..." Shining finally capitulated. "Dammit..."
Cadence chuckled indulgently. "Well, you must have made quite the impression on Twilight to have such a strong bond. How did you manage that?"
"Well, when I first expressed romantic interest in her, she said yes mostly because I was the only one outside family who she didn't have to dumb herself down to have a normal conversation with who would treat her like a fellow sophont, rather than some sort of divine being," Nefarious explained. "Comes with us being two of the three smartest sophonts in the known universe."
"Why did she not date the third?" Luna asked curiously.
"That'd be Vendra Prog," Twilight explained. "She was a villain too, but she's since been rehabilitated and is a member of Dad's harem, and Nefarious' adopted daughter."
"Spike, tell me there's some hard cider somewhere here I haven't drunk yet?" Celestia pleaded.
"Anyway, once the date had been agreed upon, I wanted to make it really special since I'd learned about some of the hard things she'd been through," Nefarious explained. "Qwark told me one thing that had long haunted her was the feeling she was the only one of her kind, so I started the date by showing her this." He tapped his equine physique. "Normally I'm bipedal, but I added a function to transform into an equine like her, complete with wings and horn, but a stallion, so she wouldn't feel alone that night. Also built a robo-pegasus-drawn carriage to take us to a castle I built on the side of the mountain for ballroom dancing." He glanced out the window. "Looks a lot like that place over there, but without the hanger-on houses," he said, pointing to Canterlot in the distance. "After that, we went to the dinner reservations I got for us at a fancy restaurant."
"...altered your entire physique to give her comfort, and built an entire fairy-tale castle just to try and give her a piece of a home she didn't remember at the time?" Cadence clarified. She rounded on Shining Armor. "Shiny, don't you dare try to get between them!"
"Hey, anyone who goes that far to try and make my LSBFF happy is alright in my book!" Shining Armor offered defensively. He offered a hoof to Nefarious. "Welcome to the family. Good luck keeping your sanity."
"What's that supposed to mean?" Twilight demanded irritably.
"That he knows you?" Nefarious offered teasingly as he accepted the hoof-bump. "No worries about that though, Knight-boy. I was insane long before I met Twilight."
"Though if part of you getting together was because you were both so intelligent and creative, I imagine things in the bedroom are quite...interesting?" Cadence asked carefully. "I mean, especially with the Villain-Princess dynamic."
"Well, there was that one time we traumatized Cthulhu," Nefarious began, ready to relate details of a particularly exciting interlude between the pair.
"Oh great Earth Mother, swallow me now so I don't have to hear this!" Celestia prayed fervently.
The floor of the library ripped open beneath Celestia and Luna, and black, thorny vines wrapped around them and dragged them into the ground before closing around them.
"...well that was convenient," Pinkie Pie observed playfully.