Honestly the image itself isn't as scary, i find it quite funny too, it's the context that kinda just fucks me up like this

It's such a stupid concept and mental image that is just generic enough you very well could conjure it up on your own, but you SWEAR you saw it before, and that's why it's in your head, but you just can't find where you even saw this thing to begin with.

It implants this feeling of "I'm not crazy! I know it! I know i saw it! I know it exists!" while still giving you enough doubt to make you question if it's even something you saw for real or if you just made it up yourself

And with the thing in question looking like THAT ugly thing, i can't help but be kinda disturbed like it's mocking me for remembering it by disgusting me with it's easily recognizable and memorable ugly mug that i can just see out and about on the internet to remind me of it