I believe they were discovered after one of the button codes (more characters in multi) was officially released on the Goldeneye website. Banjo Kazooie has the

I believe they were discovered after one of the button codes (more characters in multi) was officially released on the Goldeneye website. Banjo Kazooie has the same thing, a ton of things in the game are accessible by entering special codes in the... sandcastle? Sorry it’s been a while