As reported by Nintendo Life, Diddy Kong's render on the Nintendo Japan website has randomly been updated, sparking hopes that he might be making a return sometime soon.
The discovery was made by Twitter user CosmoBrittany73, who Tweeted out her finding and compared it to the older render that was from Mario Party. The render can be found on Nintendo Japan's character portal for the Mario series, with Diddy Kong and Donkey Kong appearing at the bottom.
Looking at the new image compared to the old one, there is a clear difference in render quality. The big difference is the quality of the fur on Diddy, which has been updated to look more realistic. His pose is the exact same as it has been for several years now, most recently appearing in Mario Kart Tour, but the fur is brand new.
Looking at the other character's on the portal, there's a mix of new and old renders. Mario's render seems pretty updated, but Luigi's is still a pretty old one. This makes it even more curious, as neither Donkey Kong nor Diddy Kong has had their own game in quite some time, and yet their render is updated before Luigi and other Mario characters.
The most boring possibility is that this is literally just a render update and nothing more. It's a little random, but it makes sense for Nintendo to go back and update their characters from time to time.
A realistic expectation is that this is something to do with the Donkey Kong expansion that's currently in production at Super Nintendo World. A locked door in that park has hinted at Diddy and Donkey coming to the park, so it could be a render that's shared between the two sites.
Some fans are going a bit wilder with their theorising and think it could be something to do with a brand new Mario Party, or even a new Donkey Kong game of some kind. It has been some time since Donkey Kong Country: Tropical Freeze, so perhaps it's time for the duo to return.