If you’ve ever been to a dentist’s office, there’s a good chance you might associate them with little aquariums. Well, it turns out that link is also how we got the classic After Dark Fish screensaver that PC users enjoyed in the early ’90s.

That’s according to Ed Fries, co-founder of After Dark and former vice president of Game Publishing at Microsoft, who spoke to Jesse Petrilla about it recently. Reportedly, an artist approached Fries as she was working on a scene set in a dentist’s office, and “she wanted to have an aquarium in it because there’s always an aquarium in a dentist’s office.”

“And she said, is there any way I could have a little part of the screen and have fish move in it?” Fries supposedly told them, “I’m a video game programmer. I can make fish move on the screen. Give me the fish, and I’ll make them move.”

Fries made a looping animation for them, then went back to the artist to ask for some bigger fish characters they could use for “this crazy idea” they had. With the new larger fishes in hand, Fries then stayed late at the office and turned his entire screen into one big aquarium.

This screensaver started life as stills of fish moving, with parentheses on screen to mimic water moving, and o’s to represent bubbles. Fries says that people in his office asked for copies of the screensaver, “and pretty soon when I’d go home at night, I’d see it running on all these computers around the office, which was fun. Anyway, that was kind of the start of my whole fish phase of my career, which I don’t always talk about.”

This screensaver led to the official After Dark fish screensaver that became synonymous with Windows screensavers in the ’90s. Fries was hired full-time to work on Excel for Microsoft, and he decided to make the new screensaver while learning how to work in Windows. He then started work on a Mac version of the screensaver after a co-worker on the Microsoft Word team asked Fries to do it.

This co-worker then wrote a fish editor where users could customise their fish in their tanks. “There was a whole kind of group of people at Microsoft at that time, like an underground group that made useless games, useless stuff. That group, which I was part of, called themselves bogus software.”