Your fave is problematic: Alphys

Why?

Well, precisely because of this!

Undyne was a friend, just a friend, there was nothing there, surely. Like- why would she of all people want to sink down to Alphys' level? She's way out of her league anyway… but that's what was so hot about this.

"O-O-Oh, Un-Undyne. I feel really exposed…" Well of course she did, wearing her polka dot dress, only the polka dot dress, legs splayed open and tail swinging back and forth with an anxious blush on her face. Holy cow, she was already dripping just from looking at the deep blue silicone of her specially hand-crafted dildo.

"Don't worry, Alphys. I'll take good care of you." A mechanical voice crooned gently, tinted with just the slightest feminine tone. The reptilian scientist tried not to look too closely to the owner of such a pleasurable device, but it was too difficult and brought her to stare awkwardly up at the creation that was Mettaton. "Alphys, no need to look so petrified, just relax. How about this, darling, let's turn you around, on your claws and knees."

The royal scientist shifted awkwardly, her dress catching on her tail as she tried to move and obey Mettaton's commands. Wait, no, Undyne's commands. Alphys shivered, yes, that was it. The thought of having Undyne commanding her to get on her hands and knees made her body tighten and cheeks burn. Now, not being able to see Mettaton, it was easier to put him out of her mind again.

"Alphys- you look so cute right now."

Alphys gulped down a gasp, the most nervous expression in place. That was different, very different. Mettaton's voice wasn't there, that mechanical voice box, instead, it sounded like a particular fishy knight, as if Undyne was right there behind her. Then there was the coldness of metal, no, scales, trailing up her things, massaging the base of her tail then trailing teasingly along the lips of her very wet pussy. The reptile was choking on her moans, mouth salivating and chest aching.

"Mmm, Alphy, you better not keep your sounds to yourself. I won't know if I'm making you feel good!" Undyne muttered gently, fingers stroking the opening of the scientist's entrance.

"Y-Y-Y-Yes Undyne! I-I apologize, you- you make me feel- real- real good…!" Alphys managed to stutter out, curling her back to try to coax the fingers inside of her. Undyne wasn't cruel, however, and didn't make her wait another moment before softly pressing two digits into her. "O-Oh gosh- Undyne, Undyne!" Those cold fingers curled into her, pressing and rubbing in all the right places. Alphys didn't dare hold back her sounds this time, cute little moans bubbling from her lips of a particular fish lady's name. Another finger found its way to teasing, this one, instead, circling the reptile's clit and flicking with a sort of ease. This was all too much too fast, holy fuck. Alphys was near to whimpering now, her insides heating and tickling harshly, oh god, she was going to climax soon.

"N-N-No, Undyne- please- I- I- I…."

"What is it, Alphys? What do you want?"

The reptile whimpered, her slick tongue flicking out briefly to wet her dry lips. "I- I want- I want you to f- fuu- mn. Fuck me… please…"

Undyne chuckled rather boisterously from behind her, finding this situation rather humorous. Even with the amount of embarrassment that Alphys felt, it was all melted away when the tip of the thick dildo was rubbed against her dripping cunt. "O-Oh, Un- Undyne, I…" It pressed in easily, the first half of the device already stretching the reptile beautifully. "Oh my- g-god! Undyne! Ooooh-!" Her moan tattered forth as the rest of the dildo pressed its way into her.

Alphys looked a sight, dress hiked up to her hips, tail propped up against her back, cheeks bright red and tongue lolled out with eyes dazed and closed as she was screwed. Her thighs were wet from her juices and the squelching sounds of her being fucked only made this whole situation ten times hotter.

Cold, met- scaley hands gripped the reptile's hips, one cupping her ass while the other played with the playful tail. "Alphys- you're so wet, I love it. And so soft- I wanna fuck you forever… you're so adorable…"

The royal scientist was grinning giddily, eyes blown wide and her orgasm rushing towards her once more. Oh god- Undyne- yes, please, she begged. "Please- puh- pu- please- Undyne, make me c-c-cum-!" Undyne was so intense, obeying the plea with full force and pistoning the thick dildo into the pleading reptilian's pussy.

It took not even three more thrusts to make Alphys literally scream, the sound choked off with garbled sobs and the plea for the fishy knight. The waves of euphoria passed gently, however, and she felt dreamy for the longest time. Hell, she didn't even notice the feeling of the dildo slipping out of her and the awkward silence.

Eventually, she was brought back, and Alphys awkwardly sat up, pulling the hem of her fancy dress back down as she faced Mettaton once more. Oh dear, he looked so awkward, the dildo still attached to his lower rim and dripping with her cum. "Alphys- darling, was that sufficient?" The now very robotic voice lulled.

Alphys gulped, her blush still rising in her cheeks. "Y-Yes, Mettaton. It- it was very- sufficient…"

The robotic star shot up suddenly, arms waving ecstatically. "Well of course it was, Darling! After all, I need to be full of drama, action, and romance to get an audience's attention! That compels the show, it brings everyone together for me, the star~"

His words continued on, only bringing Alphys to sigh heavily and try not to stare at the blue dildo that still hung from Mettaton's waist.