Keep it civil, do not flame or bait other users. If you notice anything illegal or inappropriate being discussed, contact an administrator or moderator.
Please be aware that posting insults directed at users of the site is a bannable offense.
That said, a grand total of two pages of posts tagged "undertale" were uploaded by Gelbooru users, out of nine pages total. To put it another way, no one's actually spamming the posts here, they're being uploaded to Danbooru and automatically imported, as we do with all images uploaded to danbooru. In other words, calm your tits, no one's spamming Undertale posts here.
Also binderwing, do not remove tags from undertale images. This is also a bannable offense. Furthermore, just because art of something you do not like is being uploaded, that is not spamming. A certain amount of the undertale art is by Japanese artists, which is allowed here.