So there are, unsurprisingly, a few posts on this sub hypothesizing about the identity and nature of the Blue Man. However, these hypotheses generally attempt to identify the Blue Man on the basis of his depicted traits, which I think is not correct for one simple reason;
The Blue Man appeared in a dream.
Now, I think the Blue Man does happen to correspond to some external entity, but I don't think his appearance should tell us anything. I think the Blue Man is nothing more or less than the chosen form of some kind of dreamwalker who invaded Big D's dream for some purpose. What purpose? To freak him the fuck out, of course.
Consider the sequence of events. First, Big D finds a 99p