Very cool idea. The task of managing so many different characters at once and losing control of them as soon as you manage another one gets very chaotic indeed pretty quickly. And also very challenging, which I like a lot!
The graphics and music are fine, though some interactions definitely lack sound, that would have made it even nicer. I personally think it's okay to select characters with the mouse, it definitely adds to the chaos, and simply assigning buttons to each character as other commenters have suggested might have made the game too easy.
I definitely recommend everyone to give it a try!