Argonaut

Argonaut is a company that worked with Nintendo from roughly when the SNES was being made to after the creation of Super Mario 64.

Jez San's claim
Before the creation of Super Mario 64, Argonaut pitched an idea for a 3D game featuring Yoshi main character. Shigeru Miyamoto turned down this idea, but in 1995, when Super Mario 64 was being shown off, Jez San of Argonaut noticed how the game "had the same look and feel" as the game that they had pitched. Miyamoto eventually apologized for not picking up Yoshi Racing originally.

Phenomena
Because of Jez San's claim, it is widely believed that Miyamoto stole Super Mario 64 from Argonaut, although there is yet to be solid evidence of this.