Two notable instances:

- first iPod prototype --- Steve Jobs dropped it into an aquarium and when bubbles rose up noted, "there's space inside, it can be smaller". https://www.businessinsider.com/steve-jobs-threw-ipod-protot...

- iDVD --- he drew a button on a whiteboard and announced, "Here’s the new application. It’s got one window. You drag your video into the window. Then you click the button that says BURN. That’s it. That’s what we’re going to make." https://www.entrepreneur.com/living/how-steve-jobs-1-design-...

I'd like to think that the current behaviour of the Apple Font pallet where when collapsed into a single bar grew out of a suggestion made after discussions on comp.sys.mac.advocacy --- but he was justifiably proud when he showed it off to one visitor (per a link I can no longer find, or which is no longer up, or behind a paywall)