Interesting concept of using a toothbrush and a vibrator to build a small fun robot.
Simply connect the two leads from the motor to the battery – instant vibration.
There are plenty of examples of things like this pre-existing. There are animals and plants that use ratcheting bristle motion for locomotion and seed transport (wheat stems come to mind). There are also countless industrial uses– little strips of angled-bristle materials in copy machines and laser printers that use this process in reverse, to move *paper.*