UPDATE: The original source has removed the tweet in question, and has apologized in subsequent tweets for the previous report to “avoid miscommunication”.
ORIGINAL STORY:
While Nintendo’s Mario spin offs have traditionally been the domain of the Mushroom kingdom and all of its inhabitants, in recent times, we have started to see some more crossovers with other Nintendo franchises. The excellent Mario Kart 8 and its Deluxe incarnation, for example, include Link from The Legend of Zelda, Isabelle from Animal Crossing, and the Inklings from Splatoon as playable characters.
Now, Link might be getting ready to cross into another realm—the tennis realm, to be specific. Dataminers have unearthed evidence in Mario Tennis Aces’ code that Link is set to be added to the title, with his Champion’s Tunic, traditional green tunic, and Dark Link tunic available as the various costumes that will be available for him. If true, this marks not only the first non-Mario character in Mario Tennis Aces, it marks the first non-Mario character in any Mario Tennis game, period.
As of right now, this is not officially confirmed, though as mentioned, evidence does exist thanks to the Mario Tennis Aces Club having shared the data they have found on Twitter. Hopefully an official announcement is made soon.