https://www.nintendo.co.uk/Iwata-As...the-Night/4-Gestures-in-the-Night-222196.html
Koizumi: Right. I was really having a hard time figuring out how to make things move in that scene. I was working away late at night, and all of a sudden Miyamoto-san comes up behind me and starts doing these gestures.
Iwata: Gestures? (laughs)
Koizumi: (Making a "balancing" gesture) While he was saying, "Not like this... But a little more like this."
Iwata: (laughs) So Miyamoto-san was trying to tell you how Mario should move through his own gestures?
Koizumi: He'd be saying things like, "His feet should move like this here, and the focal point is right around here..." This was around 2 or 3 in the morning, and pretty much all the development staff had already gone home. So it was just Miyamoto-san and me in the office, and he starts showing me how Mario is supposed to swim while saying, "It's not really a breast stroke, and not a crawl, but something like this maybe...?" And he was completely sprawled out on the desk doing these swimming motions. (laughs)
Everyone: (laughs)
Koizumi: I really should've snapped some pictures of him doing those gestures. (laughs) But when I looked at him there and noticed he wasn't a bit embarrassed, I thought, "This is the work of a true director." And something I realised later is that drawing up instruction sheets for 3D games is extremely difficult.
Iwata: Unlike with 2D games, it's definitely a lot harder to explain what you want on paper when it comes to 3D.
Koizumi: Yes... Other than Mario, I was in charge of player design for a 3D Zelda game, and when looking at how the feet run, or various other small details, I really felt like my experience with him during Mario 64 taught me how important it is to get those little details right.
Iwata: It sounds like Miyamoto-san's late night gestures really helped it sink in.
Koizumi: You could say that. (laugh)