What do you mean this didn't happen

Look I’m excited about this one so this here is her info dump.

The Nyangineer (Algerna is her real name. Like Flowers for Algernon.)

Algerna runs the core and has since Gaster’s accident. She actually worked with him to help him build it and was very close with him. However, when he started his next experiment (the one Entry 17 references) she left his research group because she had a bad feeling about it. When things went wrong she was left with some nasty survivor’s guilt (”I should have stuck with him, I should’ve sabotaged the machine if that’s what it took to stop him from going through with it”) and as a result immersed herself in her work. Ever since then she’s been working to reverse the effects of the machine, tinkering in the lower core to reroute its energy as it’s the only power source strong enough to power the machine she made to reverse Gaster’s fate. She talks to the air a lot; mostly to herself but also to him because she knows he’s listening and would probably appreciate being recognized, even if it’s a one-way relationship.

In game you’d hypothetically meet her as you wander the core. She has bad attack and good defense, which could be lowered by taking advantage of her misophonia. Singing to her would make her defense drop as she gets uncomfortable, plugging her ears, and getting emotional. But once her defense hits zero she’d lash out and one shot the player. Like sans, She’d know when she’s killed you before. But in actuality it would take you less time to just chip away at her then to drop her defense to zero, so it’s very much an asshole move anyhow.

For all the pacifists, it’s a meme to spare. Reference memes to her and she’ll get super excited. 

Her attacks are claw swipes that warn you on what side of the box she’ll strike, a pencil attack where you have to avoid the lines she draws, and an electricity attack where you’d have to avoid jagged bolts of electricity.

When sparing her she’d use her pencil attack to first draw a heart around the character and further spares would result in her drawing memes, which would probably be greyed out (or blued maybe) in more complex ones. (So tl;dr if you were sparing her you would not take damage from her unless you tried to.)

She’d have a theoretical optional postgame a la the true lab (but not necessary for a pacifist run) where she’d enlist your help in the lower core solving puzzles (”I’ve been doing at these things for so long I can’t solve them anymore”) while she makes final adjustments to reverse its energy flow. She follows you around and could be conversed with for backstory. She’d also know what type of run you were doing. 

If you were to help her in a pure pacifist run, there’d be a scene in the credits where she brings back Gaster after everyone has left the underground (cliffhanger!), but in a tainted pacifist run the machine would fail and she’d meet the same fate as her colleague.

...But at least she’d be reunited with him, right? 

The head engineer in the core is a dweeb pass it on.