In this clip, you'll see "a classic Super Mario Bros. level recreated in 3D, using the Doom engine." Though the skin may not be perfect, it's definitely a conversation piece to say the least. (From Techeblog)
That's funny, but a little late. Some of my fondest memories come from the Alien TC and the Evil Dead TC for Doom. Later, with Duke3D, they had "The Gate" which borrowed heavily from Total Recal, and Redrum II which was a giant Overlook Hotel from The Shining. Good times.
Cool video! Amazing to see what people can do with the Doom editor. Played around with it a long time ago and while it has its limitations, its fairly easy to use and alot of fun. I posted a video (from the same guy?) you might like as well here. It also has a star-level in it.
Probably one of the newer source ports, like ZDoom or Doom Legacy.