Spector cites an amusing anecdote from Ultima 6’s in-house testing: "…on Ultima VI, which is kind of where I realized that all this improvisational stuff could really be magical. It was unplanned, kind of a bug. There was one puzzle where the Avatar and his party came up on one side of a portcullis and there was a lever on the other side of the portcullis that you had to flip to raise the portcullis and keep on making progress. I watched one of our testers, a guy named Mark Schaefgen, playing in that area. And he didn’t have the telekinesis spell, which was the way to get past that portcullis. I was sitting there rubbing my hands together going ‘oh ho ho, he’s screwed, he can’t do it.’
He had a character in his party named Sherry the Mouse. You can probably see where this is going. The portcullis was ‘simulated,’ and here the air quotes are around simulated, simulated enough that there was a gap at the bottom that was too small for a human to get through, but not too small for Sherry. He sent Sherry the Mouse under the portcullis, over to the lever, she flipped the lever, and then the rest of the party went through. And I fell on the floor. At that moment I just said to myself, ‘this is what games should do. We should start planning this, not having it happen as a bug.’ That was where I realized this was really powerful."
It was things like this that make the Ultima series stick in my head to this day. :)