One of the ovals is a puppet, and it is controlled by the mouse, probably using a technique like the "new version of BG" in the course documents page of Blackboard. It can move around the screen, spin in different ways, maybe change colors, or shades of color.
The other oval is autonomous. Your goal is to give it recognizable emotions with respect to the other oval.
For example, it could be an affectionate puppy-dog oval. I think a puppy dog would follow the other oval around, it would slow up gradually as it approached, and then gently bounce off and approach again.
Or it could be an aggressive guard dog, speeding toward the puppet, and hitting it hard. This would be a better effect if the puppet were jarred by the collision. Maybe it could be knocked off course, so that you would have to use the controls to keep it from moving away.
A noisy lapdog could race in circles around the puppet, possibly changing colors and/or pinwheel rotation to indicate pleasure or anger.