Carefully detach the unicorn horn and the ears from the hat with a thread ripper.
Cut some craft foam the same shape as the ear but a little smaller. We'll use this to attach to the servo.
Give the craft foam a bit of character with a curved shape and stitch it to the servo attachment piece.
Slip the servo and foam inside the ear and sew it closed across the bottom.
Repeat with the other ear.
Attach some alligator clips to the three wires and hook them up to the Circuit Playground. Move the ear back and forth with the joystick and play around with proper placement on your hat. I ended up adding another little stitch to make my ears flop over a bit more.
Once you're happy with placement, sew and/or glue the servo in place on the hat, hiding it inside the fabric. Don't sew the EAR in place -- it should be free to move! Just attach the servo.
It's alive! Hooray! Go find someone and show off a bit.
Not done yet though.. a magical animatronic unicorn must have a glowing horn. (I think that's some kind of law) Luckily our Circuit Playground comes equipped with lots of lights...