Translated by the excellent Shmuplations, the conversation between Miyamoto and Namco’s Masanobu Endo originally appeared in the February 1986 issue of the Japanese magazine Famimaga and is believed to be the oldest verified Miyamoto interview anywhere online.
In it, the two designers discuss the games they are currently playing, Miaymoto's hopes for Mario's future and even the music he was into (spoiler alert – it's bluegrass, but if you know anything about Miyamoto, then that shouldn't be much of a shock).
A bit of background on Endo (simply because we assume you're all aware who Miaymoto is) – during his time at Namco, he worked on arcade titles like Xevious and The Tower of Druaga. In 1986, he had left Namco to establish his own studio but would still work closely with his former employer.
The interview begins with both developers praising the work of the other, with Endo stating that Super Mario Bros. – which had launched the year previously – was "the most interesting game last year". Miyamoto returns the compliment by singling out both Xevious and Druaga, calling the latter "impressively well-made".
Endo then mentions Donkey Kong Jr. Math, saying how he "always" wants to play it. Miaymoto reveals that it's "super popular among the staff at Nintendo, too," pointing out that it's a "simple" experience but "turns into a real rip-roaring good time when you play it with 2 players".
Released on the Famicom on December 12th, 1983, the game was designed by Toshihiko Nakago. It would arrive in the west in 1986, but was considered an 'old' title in Japan by this point.
Later, the pair discuss the complexities of game design, and Miaymoto jokingly admits that he feels he isn't liked by the programmers who work with him:
"I'm disliked by the programmers. Of course we decide the main, important aspects of the game beforehand, but as the development goes on there are lots of small details we update. So they say about me, "Hey… if you work with Miyamoto, you'll never know when you're done. Watch out, you'll find yourself overloaded with a mountain of work at the end!""
We'd recommend you give the whole interview a look and take some time to browse the Shmuplations archive – it's a truly remarkable collection of translated interviews.