As Alphys will happily complain given half an opportunity, Mettaton does not like anime. He dislikes it the same way he does everything: loudly and dramatically.
If you're willing to listen to fifteen minutes of increasingly ostentatious sighing, he will eventually explain this dislike to you. "It's so... unnatural," he would say, or something to that effect. "It takes everything good about humans, their energy and their enthusiasm and their liveliness, and tries to capture it in flat drawings."
Then, as if realizing he was acting like a real person, he'd shudder theatrically. "And those eyes! Honestly, darling, it's enough to give me nightmares, and I've met Temmies."
Despite Alphys' best efforts, Mettaton would not be swayed on this subject. Animated humans were just much less interesting than the real thing, even if they had cat ears and magic kisses.
At least, that's what he tells Alphys whenever she invites him to watch her latest ridiculous garbage. When he's alone, he's rather less inflexible. (This should come as a surprise to absolutely no one. One of the rules of drama is that the person who complains the most about something is a secret fan, so really Mettaton is just living up to expectations.)
Anyway, it's not like he has a hoard of DVDs hidden at his house. It's just that every now and then, he likes to relax by watching some of the only anime he finds halfway passable.
And if he posts fanart online, well, he was never one to do things halfway. He's always at his best with an audience, whether he's posing for his latest movie or relaxing at home. It's not like his account can be associated with him in any way.
He finds that leading a double life is a lot more fun without the constant guilt hanging over his head.
But because nothing can ever be easy for Mettaton, it isn't long before things stop being simple. As it turns out, he and Alphys have relatively similar tastes in anime. And if that wasn't horrifying enough on its own, she evidently spends enough time on the internet to have found his art.
So when Mettaton logs on to post his latest piece, he finds a comment from one ALPHYS. All it says is, "This is so cute! I love this show," and Mettaton is distantly impressed that she didn't go on a rant about her favorite characters.
The rest of him is consumed by internal screaming.
Eventually he gets past his initial instinct, which is to delete his account and burn his computer, and starts thinking about possible solutions. He could just ignore the comment, but so far he's responded to every single comment on his work. Ignoring this one would just be suspicious.
He eventually taps out "Thanks, beautiful! :)", hitting post before he can think better of it. Then he slams the laptop shut and walks away. His fans will want to see him, after all, and it would be a shame to keep them waiting.
He has a delightful time listening to his fans talk about how amazing he is. He comes back refreshed by the experience, and he logs back on with barely any hesitation. To his relief, ALPHYS has left no more comments or shown any sign of recognizing him, so he can post his latest masterpiece in peace.
When she comments on that one, it's that much easier to think of a reply, until it's almost a game: how long can he keep Alphys in the dark as to his identity. He thanks her for her kind words, even flirts with her to see her flustered reaction.
They've been going back and forth with this for a few weeks when Alphys calls to invite him over to watch the long-awaited Mew Mew Kissy Cutie movie. Mettaton sighs dramatically and shakes his head. (Alphys may not be able to see it, but it's the principle.)
"Alphys," he says patiently. "I've explained this to you before: anime is trash. Mew Mew Kissy Cutie is especially trash. Why would I want to sit through a full movie of it?"
"O-oh, I just thought that since you were p-posting that art..." She trails off expectantly.
Mettaton forces himself to laugh. "I'm flattered that you'd call my movies art, but what about them would possibly make you think I'd enjoy this garbage?"
Alphys snorts. "I'm o-obviously talking about the fanart you post online. You know, of that so-called 'trash'?"
"Why would you think that was me?" he asks too quickly. He knows he's being suspicious, but at this point he's obviously lost and is just delaying the inevitable.
"Well, you call every third commenter 'darling'. You're pretty much the only monster who'd do that," and oh look, she's not even stuttering, she's so sure of her conclusions.
Mettaton struggles to respond for a moment before he gives up. He hangs up on her, deciding to deal with this later. For now, he's decided to enact Plan A. He can always buy a new laptop, and this time of year a fire would be wonderful.
