https://bluesyncline.gitlab.io/furby/index.html: 1998 original Furby assembler source code and transcribed to assemble-able code (published in 2018 on github)
furby voices on archive.org

https://cdn.preterhuman.net/texts/engineering/Furby%252C%20Reverse-Engineered.pdf
https://patents.google.com/patent/US6544098B1/en
Furby Autopsy
https://web.archive.org/web/20190725163824/http://www.techdose.com/projects/Furby-Hacking-101/260/page1.html

Furby 2012 has monochrome-LCD eyes and multiple personalities included. It has ultrasound communication “ComAir” for inter-Furby interactions and app connection. It can connect to Furby Party Rockers “mini-furby companions” and later Furby Boom, which is based on 2012-model. Furby Boom can connect to Furblings exclusively and to Furby2012 over ComAir. Party Rockers and Furblings have no moving parts, “holographic / lenticular” style eyes with a backlight LED for illumination. Party rockers have tactile buttons for interaction, Furblings do not react to touch and can be used with Boom only.

2012 teardown.pdf on adafruit
https://poppopret.org/2013/12/18/reverse-engineering-a-furby/

https://habr.com/ru/articles/166377/ and https://github.com/iafan/Hacksby

Furby Connect (2016) has colour-LCD eyes and nRF51822 for Bluetooth connection inside. The app “Furby Connect World” has been discontinued: To Download and use, see https://github.com/Furby-ReConnect/Furby-Connect-World-CDN. For troubleshooting, read this tip.
FunFact: feature of multiple personalities was scrapped in development. 7 unused personalities are still in NAND (unused audio files).

https://github.com/Furby-ReConnect and https://github.com/Furby-ReConnect/Furby
archived original blog post of Furby-ReConnect

https://www.pentestpartners.com/security-blog/new-furby-teardown/
https://official-furby.fandom.com/wiki/Furby_Connect/Hacking

CCC talk: Don't Feed Them After Midnight: Reverse-Engineering the Furby Connect
Reverse Engineering Furby Connect's Bluetooth Protocol and Update Format and read the docs
https://furby-science.tumblr.com/post/190181429954/hacking-your-furby-connect-the-quick-and-easy-way
Python tools for handing Furby Connect DLC files
https://pdjstone.github.io/furby-web-bluetooth/ FurBLE - Furby Web Bluetooth Demo
https://github.com/swarley7/furbhax
https://github.com/martinwoodward/pyfluff Python rewrite of Bluefluff

#TODO: describe replacing nRF in Furby Connect

https://github.com/matteoferla/pyfurby
archived replacement-PCB schematics

https://www.instructables.com/Control-a-Furby-with-Arduino-or-other-microcontrol/

Open FURBY (based on Furby BOOM which is similar to Furby 2012)

Check out modified Furby skins/furs by “The Drunken Witch Co.”, e.g. on TikTok or Instagram

Also search on reddit /r/furby

Hack those Tamagotchis! https://natashenka.ca/