There were a lot of struggles here.

• The Echo Dot didn't quite fit in the enclosure. I had to remove the back to make it a little slimmer. This was ok as I was using the headphone out and the back contains the unused speaker. I also had to trim some plastic to get the circle to fit flush with the inside of the front.
• When I closed it up at first, I discovered that the microphones were blocked entirely and Alexa couldn't hear me. I had to drill some holes, but I didn't do a great job and ended up drilling some poorly placed holes.
• I was disappointed with the movement of the mouth, which is far too little even from off to max. I tried cutting the plastic a little to remove some of the resistance, but it still wouldn't open as wide as I wanted.
• It took a bit of probing to find the 5V test point on the Echo from which I could draw power to supply the ATTiny and motors.
• The firmware, and specifically the audio processing, was just a pain. It took way too long to find an algorithm that would work.
• Similarly, I went from most difficult to least difficult option for sensing the awake-ness of the Echo. If I had started with the photoresistor I would have saved myself an evening.

Nonetheless, It all came together, and it works. I'm having fun finding the best songs to demonstrate the awesomeness of this mashup, and I'm happy with how clean it looks and works.