How do you tag a picture that mimicks the original art style?

maybe "style_parody"?

I thought that too, but the wiki for style_parody is rather confusing. Its definition before the current one would suggest this isn't what that tag is for "Parody in which an artist tries to use another artist's drawing style on a character created by a third artist."

That's why I'm asking.

Convincing fake, maybe?

official_style