It's a NFE that I only occasionally remember, but I will say that I find the drool and sleepy eyes a tad more memorable than Vileplume's happy face (Though granted the smiley face itself makes it somewhat sinister in its own right)
It's amazing. The concept of an alien virus is just really cool, it looks great, and has a great battle theme. And in ORAS you even battle it in space which is awesome. One of the best mythical Pokémon.
I appreciate the irony in it goin' from dipshit to genius upon evolution. But for some reason, I find it kind of ugly. I've always preferred slowbro. That said, with how vampire-esque galarian slowking appears, I think there's a high chance I'll end up likin' it when that form is revealed in full.