The original Furby was interesting on this front, I have one controlled by a Pi Zero using a motor controller and LED driver board (you need an LED for the cam position sensor, and this way I could backlight the eyes with RGBs too). Every expression the thing can make is driven by a single motor via a series of gears and cams, so it's pretty straightforward to get up and running. The main issues are that clearance is really tight and the gearbox is pretty noisy.

My eventual plan is to hook it up to an LLM and use it like the world's most uncanny Alexa, but there's an issue with the audio board I've not got around to fixing yet. Got a bit sidetracked by the server software which I'm using as an excuse to learn Cats Effect properly.

The Furby + LLM is an amazing and hilarious idea. Please post about it if you do this, would love to see!