Hmm, I didn't catch that. Didn't we run into that somewhere before? Or am I thinking of the TMS0980? I know the SR16 calculator removed one instruction and used that spot in the PLA to modify one of the built-in opcodes.
I'm pretty sure the Mattel Classic Football 2 CPU is a Winbond 4-bitter, in the same family as the W541E260. The pinouts line up perfectly, but it looks like there are a lot of members in the family, so I'm not sure which exact one it is. Interestingly, it's EEPROM. I haven't found enough info on the chip to see if it can be read.