Super Mario Crossover.

[NatureBoy]

Someone at Newsground did this Flash game where you can use either Mario, Link, Billy from Contra, Simon Belmon, Mega Man or Samus on the original Super Mario Bros side scroll game. http://www.newgrounds.com/portal/view/534416

[morsdraconis]

It's not only on Newgrounds, but it's silly and fun. Certainly worth 15 minutes or so. :)

[bdoughty]

Because I am a stickler for accuracy. Newgrounds is just a host of the old version 1.0 (amongst numerous other sites) which was released back in 2010.

The creator (http://www.explodingrabbit.com/wiki/Jay_Pavlina)

The newest version is 2.1, which is hosted at his on site and has new characters, skins, difficulties, etc. (http://www.explodingrabbit.com/games/super-mario-bros-crossover)

Also a trailer on the 3.0 version.

[JeffHCross]

Newgrounds still exists? Talk about a flashback.

[GatorfanStovy]

Just no again just no.