Sean decapped the 1st-gen Mattel handhelds. Actually that's old news but not well known, he did those a few years ago. Just that the opcodes weren't figured out until now, and now the MCU they're on is finally emulated in MAME. He made a webpage covering this, read more about it over there if interested! https://www.seanriddle.com/firstmattelledgames.html
I think this plus PPS4/1 covers all Mattel games that were on Rockwell MCUs. There are a few unemulated Mattel LED games, but on different MCUs. Sub Chase and Armor Battle are on a Hitachi MCU, and IIRC Bowling and that weird Alien detection toy are on COP400.
Screenshots (I hope the forum allows 5 in one post...):