This is shaping up to be an unexpectedly cute day for PC games. On the heels of Overwatch's new hamster hero, and from the far, far end of the spectrum, comes Doom: The Golden Souls 2, a total conversion mod for Doom 2 based on SNES classic Super Mario World. I realize that's a bit of an odd pairing, but trust me when I say it's pretty convincing. See for yourself:
The sound and art are fantastic, but it's the sheer scale of Doom: The Golden Souls 2 that really impresses. The mammoth mod sports several dozen levels connected via a world map styled after Super Mario World's overworld. Levels generally follow the locales of Super Mario World, but there's still plenty of Doom flavor to them, to say nothing of a few awesome wildcards. You can select and replay any level from the world map by walking over that level's teleporter.
Levels are filled with classic Doom enemies as well as rip-and-tear renditions of Mario baddies like Piranha Flowers. Nearest I can tell, each cluster of levels is capped off with one of the seven titular golden souls, and you'll collect hundreds of gold coins in the levels leading up to them. There are even flagpole checkpoints, which is a nice touch.
Doom: The Golden Souls 2 was made by Andrea "Batandy" Gori (along with dozens of contributors), who also made the original Golden Souls mod back in 2014. You can download Golden Souls 2 here, and you can get the necessary mod loader, GZDoom, here. You'll also need a copy of Doom 2, which you can get in the Steam Summer Sale for a buck.
To play Golden Souls 2, find Doom 2's IWAD file (if you're going through Steam, just browse its local files via game properties) and put a copy of it in a new folder. Next, download and extract GZDoom in that same folder. Now do the same for the Golden Souls file. Finally, find the Golden Souls PK3 file in that folder and use GZDoom to open it by dragging the PK3 file onto the GZDoom launcher. If all goes well, you should now be playing Doomario. If you run into any trouble, I recommend this setup guide from YouTuber IcarusLiv3s.