I was one of the three Electrical engineers on Barney (and the ActiMates product line). The three of us divided up the system design, radio and radio protocol design, PCB layout, and a bunch of other items. We spent a few weeks bringing up the factory in China.
I wrote the firmware for Barney, including the radio code and Co-designed the engine used for interactivity. It has a nice design in that the engine could be reused for other products.
I designed the protocol between the main MCU, and the voice chip, and wrote all the code for the voice chip.
I remember the Xerox work and was quite pleased that they weren't successful in getting it to say arbitrary things. The folks that own these properties are rightfully quite vested in the characters not saying or doing things they didn't authorize.