A group of fans is currently hard at work on bringing the indie freeware classic Cave Story to the Sega Mega Drive/Genesis (as spotted by @dantemendes on Twitter).
Originally released in 2004 for home computers, Daisuke Amaya's indie Metroidvania was later released on a wide variety of consoles including the Nintendo Wii, DSi, 3DS, and Switch. The game follows a character who awakens in a cave with no memory of how they got there and eventually sees them befriending a community of bunny-like creatures called Mimigas in order to put a stop to an evil doctor's plan.
Andrew DeRosier is leading the development of the Mega Drive/Genesis port/rewrite, with altiereslima, tilderain, and Nasrin Atiyeh also listed among its contributors.
According to the project page on Github, the "main story" of the game is already finished, with only bug fixes and some additional features remaining. It is currently at version 0.8.0, with the last update (from February of last year) adding simplified Chinese and Korean while addressing a few graphical glitches.
If you want to try it out, you can grab the latest version from the project's "releases" page. It should work on most emulators as well as original hardware.