vSv Entertainment Team (aka Clavera) appears to have created a mercurial Super Mario Bros. editor. His/her Super Mario Bros. Fusion project uses themes to change the enemies and tiles to make Super Mario Bros. remixes.
Take a look at a fusion of Super Mario Bros. and Zelda II: The Adventure of Link.
Ironknuckle takes too many jumps on the head to defeat, but vSv Entertainment Team has an interesting idea. Thanks for the tip Reid!