In various classes they teach you that there’s no real difference between motors and generators, it just depends on which way the current is flowing. This short video really shows that principle, as well as the strength of these little stepper motors.
I was trying to level out the X-carriage yesterday when I noticed this effect. These motors are completely mechanically separated from each other. They’re just connected electrically, through the connector block you can see in the middle of the video. Turning one of the Z-rods turns the other, with a surprisingly high degree of efficiency.