What are dream-characters exactly? Are they like puppets that play along a script? If there is a script, do they all react the same to similar situations? Who decides their actions? I’ve read a theory they might be regular (non-lucid) dreamers.
Dream characters are just basically random people in your dream. Once you become lucid you are able to control them. I don’t think they follow a script. If they do then your subconscious is the director.
By random, you mean made up randomly? The mind can do that, fabricate new people from scratch? I can’t remember whether I’ve ever seen a completely unknown person in a dream. But from the sound of it, they are lemmings to be used or abused. And abused they will be if they give me any more attitude once I take over. Mwahahaha…
I think I’ll take part in the experiment, I have this gut feeling LD is going to pick up very soon and this will be my goal: to find out more about DCs.
If you’re looking for a psychological answer, Wiki up “Jung” and his opinions about dreams and DC. In particular, his work with archetypes.
Continuing the metaphor, every play has a purpose, a message. What message does your SC have for you, using DC as puppets/actors?
Tell one of them to take you to your conscious (or subconscious) and you two can have a little chat and figure things out. 
They are like dream rocks or trees. Part of the dream imagery. Sometimes just part of the scenery.