[On AO3 I could play with the HTML and have hover notes on some lines (and also have the skeletons actually speak in their fonts), but since is a living fossil of a website you'll have to scroll to the bottom for the translation of the French lines. Sorry for the inconvenience.]

It was that time again when Mettaton took a couple days off to visit Alphys. It was usually also time for a check-up and some upgrades. His body already looked fabulous before, but now that Alphys had access to better material (back in the Underground she had to scavenge the garbage dump) he looked and worked better than ever before! And if the amount of fanart of himself he found daily indicated anything, his fans, monsters and humans alike, loved it.

Mettaton and Alphys went into the latter's lab. As she checked the cooling system of his EX form, he fully expected her to comment on how he managed to bust it again, but she was uncharacteristically silent today.

"Are you ok?" he asked. "You barely said anything since I arrived."

"Oh? Hum… J-just th-thinking, is all", she replied.

"Is something wrong?"

"B-besides your c-cooling system that I'm gonna have t-to replace again?"

And there it was.

"I-I'm ok", the reptile continued, "s-someone else I know seems to be in tr-trouble so I, hum… sent one of my d-distant cousins to take care of it for now? D-don't b-bother yourself with it. It-it'll be ok?"

"…I see."

"Ok, n-now, don't move, I have to f-fix this mess."

Of course, it was right at this second that Alphys' phone decided to ring. She let it go to voicemail and kept working.

The next day, Sans and Hisha appeared nearby Alphys and Undyne's house.

"This time I knew what was coming but it's still a bit weird", she commented.

"hey. 'takes a while to get used to the shortcuts", he replied.

"'Shortcut' isn't the word I'd use."

"a shortcut makes your trip faster and that's exactly what i'm doin'. mines are just much better."

"Can't argue with that logic…"

They walked to the front door and knocked ; however instead of being greeted by either Alphys or Undyne, they found themselves face-to-chest with Mettaton.

"Hello darlings", he greeted them.

"…Hello…?" Hisha hesitated.

"hi", Sans said. "'didn't know you were already back."

"C-come in!" Alphys' voice called from inside the house.

"S-sorry, I didn't know you were coming", she apologised once everyone was in the living room.

"i left you a voice mail", the skeleton informed her.

The yellow monster facepalmed.

"I-I forgot to ch-check my voice mails! I'm so sorry!"

"it's ok. i do that all the time."

"And, hum, who's your friend?" Alphys asked.

"that's hisha. i told her you could upgrade her phone to have storage."

"Hi", the human said. "Nice to finally meet you."

"And also meet me", Mettaton added.

"…Yeah."

"R-right", the lizard intervened. "Just g-give me your phone, Hisha, I'll be done in a second. M-make yourselves comfortable."

Hisha handed over her phone and Alphys quickly disappeared into her lab. Sans and the human sat on the couch and the robot removed the echo flower from the piano so he could lie seductively on the latter.

"So, darling…", he started, raising one leg up in the air.

"My name's not 'darling'", Hisha blurted out.

The next few seconds of silence seemed endless.

"…I mean… sorry", she apologised. "Just… just call me by name. Yeah."

Alphys came back to living room right at this moment. Mettaton quickly stood up from the piano and put the echo flower back in place.

"Seriously?" the lizard woman commented. She then turned her attention to the human and gave her her phone back. "There you go! Now you have f-full access to the two b-boxes to store your things. Also I, hum, took the opportunity to boost your RAM and-and battery power a little s-so it'll run better and longer! And I recharged it too."

"Wow", Hisha replied. "And you did all that this fast? That's awesome!"

"Alphys' skill is unparalleled", Mettaton stated. "I mean, look at me."

"B-but no matter what I do, you still find ways to overheat and c-completely bust your cool down system", the scientist said.

"So you're saying he has no chill", Hisha joked before bursting out laughing.

The robot pouted and crossed his noodle arms over his chest.

"nice", Sans commented.

"Well, n-now I see why you and Sans are friends", Alphys commented as she took a chair to sit on near her guests. "Hum, h-how do you know each other anyway?"

"Remember the whole D.I.E lab… thing?" Hisha replied once she had calmed down. "I first met him and the others there."

"Oh. Were you one of the t-test subjects?"

"No, but my brother was. I… we were supposed to go together and get more money but… well… I chickened out and he ended up going alone."

"I s-see", Alphys said.

"And later we got employed at Grillby's", Hisha added.

She started inspecting her phone and opening the dimensional box apps. Of course, for now they were both empty. To test the new storage space, she took a small pack of gums from her pocket and pushed it into the device.

"Amazing", she commented. "Still can't believe you implemented it that fast!"

"Oh, usually I c-can do it even f-faster but your phone's all in French and-"

"Oh, tu es française?" Mettaton said.

The human nearly dropped her phone.

"Vous parlez français ?!"

"Bien sûr. Pouvoir communiquer avec tous mes fans est important, alors j'ai téléchargé toutes les langues. Avec l'aide d'Alphys."

"Cool. Être un robot a ses avantages, on dirait."

"So", Alphys said, standing up, "do you guys want a-anything?"

"nah, i'm good", Sans replied.

"Same", Hisha added.

The lizard sat back down.

"i gotta go skullk about somewhere else anyway", the skeleton explained.

"And I should probably go back to the inn", the human stated.

They both got up from the couch and said goodbye.

"And thanks again for the upgrade!" Hisha thanked Alphys as she left.

Translation of French dialogue :

"Oh, you're French?"

"You speak French?!"

"Of course. Being able to communicate with all my fans is important, so I downloaded every language. With Alphys' help."

"Cool. Looks like being a robot has its advantages."

[Notes : While "tu" and "vous" are both translated by "you" in English, "tu" is more informal. While "vous" is generally more suited to speak to strangers, Mettaton seems to be the kind of person to just naturally call everyone "tu".]

[More notes : it was about time Shameless Self-Insert got to interact with Alphys! Oh, and Mettaton too.]