Ikegami Tsushinki

Ikegami Tsushinki is a Japanese manufacturer specialized in television equipment. In the mid-80s, the corporation operated a video game division that assisted with the manufacturing and programming of various arcade games, including Donkey Kong. Though not credited, the company frequently left messages in the game's ROM data indicating their involvement

History with the Mario series
Hiroshi Yamauchi hired Ikegami Tsushinki to assist Shigeru Miyamoto in developing Donkey Kong, as he had no programming experiences at the time. Miyamoto's would produce various ideas and sketches, that Ikegami would then program into the game.

The contract gave Ikegami exclusive rights for manufacturing Donkey Kong arcade boards. Due to the unexpected demand for the game, Nintendo ignored the clause and produced arcade boards of its own.

Nintendo later hired a company named Iwasaki Engineering to reverse-engineer Donkey Kong's code in order to produce a sequel. In response, Ikegami Tsushinki filled a lawsuit for copyright infringement. In 1990, a court ruling decided that Nintendo did not own the arcade Donkey Kong code. The two companies settled out of court.