Back when I was a wee lad, around 1993 or so I’d guess, my uncle’s work laptop had a trackball that plugged into a special port on the side of it. Even though laptops of the time weren’t particularly good for, well, using on your lap, it was an exceptionally nice way to be able to use a mouse in a limited amount of table space.

Edit: thank you Reddit! https://www.reddit.com/r/Trackballs/s/Lw3QQG9IY8