Use a basic servo with a straw on the end to make a waving robot. Attach the kitronik sensor board as well so that the wave can be sound activated: ask the robot to give you a wave!
Starter servo code:
Servos: SG90
Connect red to 3V, brown to GND and the orange wire to pin 2 on the microbit.
Tip: in the best setup you would drive the servo directly from a 3V battery pack rather than from the microbit to avoid the possibility of damaging the microbit by drawing too much current. Although this can cause unreliability if the batteries are not fresh: see the discussion here:
https://support.microbit.org/support/solutions/articles/19000101864-using-a-servo-with-the-micro-bit
At any rate you can certainly test it out fine for smaller projects using the 3V and GND on the microbit.
To combine this with use of the Kitronik sensor board to only wave if sound is detected, see our page on the Monk Make sensor board only this time use the sound level pin to detect some audio (start with IF the sound level reading is > 0 to test it) and then action the wave if so. If you have some test wires with crocodile clips then you can piggy back the sensor power leads on to the servo power leads: if this becomes too unstable then run the servo from its own battery pack which is the better option anyway really with servos.