Nintendo rejected this Super Mario Bros. 3 PC pitch by Doom developer id

And it led to Commander Keen!

John Romero of id Software fame just released this video of a Super Mario Bros. 3 PC port John Carmack and John Romero made to show Nintendo in order to get the license for the PC version. Nintendo would ultimately decline the offer, but id and company used the technology and wherewithal to create something of a classic in its own right, Commander Keen, which turns 25 today.