The mouse was the first laser mouse I ever used and I believe it connected with USB, which was novel at the time. It was probably the most impressive thing about the iMac for me personally.
I remember the hockey puck mouse had a ball because it was a pretty fantastic ball: it was dual toned, one hemisphere white, the other Bondi blue. As you rolled the mouse, you'd see the ball turn and have a neat color display through the translucent plastic of the hockey puck mouse.
That was my favorite part of the hockey puck mouse - it was one of those little moments of "surprise and delight" from Apple. And alas, I can't find a good video of it online.
https://en.wikipedia.org/wiki/Hockey_puck_mouse
I remember the later G3 education models my school had having a "laser" (I assume LED?) mouse.
Likely the iMac went the same way.