Anki’s Cozmo Robot was the best engineered "Pet" robot I have yet seen. I had to take one apart to replace the battery and it is an engineering masterpiece. The behaviors are pretty good also. It is about the size you are talking about but more forklift shaped then humanoid. The robot itself was pretty dumb and most of the "brains" ran on your phone via the app.

Anki went broke after the came out with a smarter successor to Cosmo. I think a biped that small would be a real challenge to make at a price point the market will accept.

Digital Dream labs bought Anki's IP and tooling and now sell Cosmo's for $400.

If you are serious about this, get yourself a few used cozmos from eBay and try to hook an LLM to the python API.

Scaling robots down to five to seven inches is extremely challenging. Aspects like energy supply, mechanical structure, and intelligent control all require significant innovation. Currently, no such startup projects are in sight, but there may be teams working secretly. For these tiny robots to mimic living behaviors, what is the core difficulty?