Bio Force Ape

http://www.lostlevels.org/bio-force-ape/

Bio Force Ape is a side-scrolling beat 'em up created by SETA for the NES. Since its cancellation in 1992, it became a famous case of Vaporware.

When a scientist and his kid are kidnapped by a mysterious villain, their pet monkey tries to save them. Unfortunately, the villain kicks the monkey and makes off with the people. The monkey then drinks some kind of super-potion that turns him into a musclebound, ape-faced, pro-wrestling humanoid. He then sets off to rescue his owners from the hordes of animal-costumed thugs and breakdancers.

The game was subject to an elaborate hoax in 2005 when a person named Paul Brown announced to the Digital Press forum that he had found a working prototype. After a Flame War erupted over whether he should dump the ROM or sell it, Paul posted a picture that revealed that he had smashed the cartridge due to all the problems it caused. The hoax started a small meme involving a supposed Blob Monster enemy that was made out of butter.

In 2010, however, the Vaporware website Lost Levels were notified by Paul Brown himself of a REAL Bio Force Ape prototype being sold on Yahoo! Japan. After buying it, the team dumped the ROM and released it onto the Internet.

Source: TV Tropes