The early 90s was a wild time for video games, and an especially wild time for PC game developers, who had to fend off the rising popularity of game consoles like the Nintendo Entertainment System.
In 1990, id Software, the game company behind the Doom and Wolfenstein franchises and the forefathers of the first-person shooter genre, struck a deal with Nintendo's then-president Shigeru Miyamoto.
id Software had recreated the immensely popular side-scrolling platformer Super Mario Bros. 3, but for MS-DOS. It took them just one week, working on the project after hours and full-time on weekends. They were looking to see if they could get Nintendo to license their PC port. You can see the first few levels of ported version of SMB3 in the video above.
If you're a details person, you'll notice a couple things are off: infinite flight, sprites, and music to name a few. Mario's a little chubbier, the sounds effects aren't exactly the same, and Mario can fly without a running start when he gets his leaf power up. Those imperfections exist because the team had to recreate pretty much everything from scratch: They had a tile editor onto which they'd redraw sprites, recreate enemy programming, and recompose maps and music.
"The timeframe was short because we already had the scrolling engine and some player code. Using a 4-head VCR we recorded gameplay so Tom could freeze frame the tape and copy the graphics perfectly," John Romero told me in an email.
The team sent the port out to Nintendo of America, then got sent up the ladder to Japan. The port, unfortunately, wasn't released to the general public. It had been rejected.
"The head guys in Japan headquarters decided they would keep the IP on their own consoles. We were told no-go and decided to make Commander Keen instead," he said. "There was no reason at all to [make the port] it if we didn't send it to them."
Later, the company was picked up by Apogee Software (now 3D Realms), a video game publisher that advanced id $2,000 to develop Commander Keen, the side-scrolling episodic platformer game that really brought id out of obscurity.
The success of the Keen series eventually gave id Software enough of a financial foothold to self-publish their much more successful titles: Doom, Wolfenstein 3D, Quake, and so on. So you can sort of thank this cute, hacky Super Mario Bros. clone for Doom's eventual existence.