I direct your attention to this post: http://e621.net/post/show/196451/
Now, according to ippiki ookami, the tags "my_little_pony" / "friendship_is_magic" do not apply to this image. Yet it is obviously fanart of my little pony, and particularly, the friendship is magic style of my little pony. Furthermore, RedFoxen gives proof that the artist even labelled it as such on the original source upload.
Now, search "my_little_pony original_character" and see many full pages of content that includes, in many cases solo/without an official character (which would apparently be the only case in which the "my_little_pony" tag should exist on the image according to ippiki), original MLP characters in the exact same vein as Maple Whisper in the aforementioned post.
In my opinion, this whole "tag only what you see" thing is getting, as noted in the title, ridiculous. At this rate, it'll get to the point at which "who knows if that orange pony with 3 apples as her cutiemark and with blonde hair and a cowboy hat and green eyes is really Applejack? Who knows it's not a random horse character that just so happens to have all those features?"
"Who are we to assume that this yellow mouse with pointy ears and red cheeks that uses electricity is actually the Pokemon character, Pikachu? We really shouldn't use the tags 'Nintendo', 'Pokemon' or 'Pikachu' on this image. Even if the artist in the original source states that it's definitely Pikachu fanart, who are we to assume that it is indeed Pikachu, even then, and not a completely unrelated character who happens to be a yellow mouse with the very same physical features as Pikachu?"
Perhaps those exmaples are a bit too extreme. Perhaps never would this site reach that point. But at this rate -- if a green pony, drawn in the style of MLP: FiM, using the naming conventions of MLP, who is as stated by the artist an MLP: FiM fan-character, is 'in no way related to My Little Pony and might as well just be a random green horse' -- then exactly what point WILL the site reach?
Let's say someone very much loves the Pikachu character, to use the same example as before. Let's say there exists many wonderful, well-crafted pieces of art of a Pikachu fan-character that looks identical to the average Pikachu as seen in official art, but has a little tuft of blue hair on his head. Let's say that said person who loves the character would get a big kick out of that art and would love the fan-character, and the skill of the artist who devleoped it, and would become a major fan of that artist if they were to find them. Maybe, by luck, they would have found the artist on e621 by searching 'pikachu' every once in awhile, and for the sake of my argument let's just assume that that would have been the only way this guy would've found that artist. But given the way things are going, what's the difference between a green pony that's obviously an MLP: FiM fancharacter and a pikachu with blue hair that's obviously a Pokemon/Nintendo fancharacter? Why would you tag a random yellow mouse with a sprig of blue hair 'pikachu' etc? And thus, the guy who loves Pikachu never does happen upon that art or artist.
I'm just sayin'. I have endured this whole "tag what you" see convention for the longest and I understand, really, what's important about it as far as physical things present in the image, even if the artist CLAIMS this creature that is by all visual accounts a male dog in a given image is actually an alien herm from the planet Zorbulon. But at this rate, it's coming to a point at which the whole existence of green tags to begin with is starting to come into question. I'm wondering at this point whether you should remove them altogether or start to rethink some intricacies of your rules.
(P.S. also there's the fact that many people might, for example, have 'my_little_pony' blacklisted that don't want to see art in this style or from that fandom at all, but don't want to have to blacklist the 'pony' tag as perhaps they may love realistic anthro ponies that truly have nothing to do with MLP, for example)
tl;dr: if a character that is obviously, visually drawn to be a fan-character from a specific IP, and the artist him/herself claims it to be so, is it really okay to defy anyone the right to tag the IP said character is based on? And if so, where does this road stop?
Updated by Rainbow Dash