So, this piece of "concept art" has been floating around since, like, May and hadn't been confirmed nor had it been proven false. I myself thought it looked very good and the designs seemed interesting enough I could see them as being legit, though some oddities like anime characters being featured and the excessive amount of oddball details shown made a lot of people assume it was merely really nice fan-art.
Today, however, a new official trailer revealed a never-before-seen NPC character who perfectly matches a character seen in the leak:
Said character is Mallow, one of the Trial Captains from Sun and Moon. The official site describes her as being an unorthodox cook and here she seems to be using Litten's Final Evolution as a makeshift stove-top.
It seems these are indeed legit, and do seem to be concept art made for the anime specifically. It's worth noting a bit into Black and White's hype cycle we had a leak of a Best Wishes character sheet, far simpler than this though, that revealed Iris in addition to Oshawott and Snivy's evolutions as well as Woobat so such a thing has happened before.
In case you're wondering what the Japanese text say, on a /vp/ thread the other day someone posted translations. Note there's no names listed, instead they're references as "Owl 3, Tiger 3, and Sea Lion 3".
1. Has a calm\cool persona
2. Tightens its hood when its upset or irritated
3. Uses its quills as arrows and vines as the string.
4. Its difficult to notice which helps it ambush foes
5. It likes to chill on Tree branches.
1. Has a wild and gusty persona
2. Fights dirty- spits ember in its opponents face, isn't above using unconventional items or means, uses Fire Spin from its belt.
4. Has a signature move called Beast\Tiger Swing???
5. That Belt gets hotter the more "passionate" it is.
1. Uses its voice to charm and or lure opponents
2. Has a elegant and welcoming nature
3. Is very playful
Personally I've seen a lot of hate for these dudes, but if you ask me they're the neatest Starter set, like, ever and I was hoping they would be confirmed and glad that they finally were. Rowlet 3 looks like he'll be the next Greninja easily, and I'm certainly using him my first time through Sun and Moon, but Litten 3 is probably my favorite Fire Starter ever now. Don't care if he's Fire/Fighting (though I'm thinking Fire/Dark), he's awesome looking.