What was the working title of the prototype that became Super Smash Bros.?

The prototype that became Super Smash Bros. had the working title Dragon King.

The project began at HAL Laboratory as a fighting-game prototype developed by Masahiro Sakurai and Satoru Iwata. Its fuller translated title was “Dragon King: The Fighting Game.” Unlike the finished Nintendo crossover, the prototype used generic, faceless fighters and did not initially feature Mario, Link, or other established Nintendo characters.

The prototype was designed around a four-player battle system and unconventional mechanics, including damage percentages that increased knockback rather than a traditional health bar. Those ideas helped distinguish the project from standard fighting games and became foundations of Super Smash Bros.

The game changed direction when Sakurai and Iwata explored using recognizable Nintendo characters. That decision gave the project a strong identity and helped turn an experimental prototype into the Nintendo 64 game released in 1999. “Dragon King” is often shortened from the fuller working title, so it is not the name of a released game or a separate Smash installment.