Super Smash Bros. was developed by HAL Laboratory, a Nintendo second-party developer, during 1998. Masahiro Sakurai was interested in making a fighting game for four players. As he did not yet have any original ideas, his first designs were of simple base characters.
He made a presentation of what was then called Kakuto-Geemu Ryuoh (Dragon King: The Fighting Game) to co-worker Satoru Iwata, who helped him continue. Sakurai understood that many fighting games did not sell well and that he had to think of a way to make his game original. His first idea was to include famous Nintendo characters and put them in a fight. Knowing he would not get permission, Sakurai made a prototype of the game without sanction from Nintendo and did not inform them until he was sure the game was well-balanced.
The prototype he presented featured Mario, Donkey Kong, Samus and Fox as playable characters. The idea was later approved. Although never acknowledged by Nintendo or any developers behind Super Smash Bros., third party sources have identified Namco's 1995 fighting game The Outfoxies as a possible inspiration.