I do think the snake needs a name beyond just "snake" and I was planning to call him Yomi, which in Japanese can mean "reading," "hell," or (more rarely, and if my memory serves) something along the lines of a sampler or preview you offer someone to pique their interest.
The other characters obviously have to be elaborations of Alyssa, Eva, Ben, etc. from the text of SICP itself. Cy could be short for Cyrus. Eva could be short for something. Not sure what.