I actually have no idea of what the serpent is except that it's a chorus instead of an individual. Which you could have figured out from the soundtrack as easily as I :P Checking youtube, it looks like most groups choreograph it as a set of people in a line. My favorite choreography of the ones I've seen tonight is here. With the additional dialog missing from the soundtrack this is the most sympathetic fall of Eve I've ever seen.

I would totally eat a forbidden apple if someone told me it would help me figure out where the sun went after it set and where my dreams go when I'm not asleep. It's no sin to be scintillating, after all.