Hi Flower
DS5 has an incredibly complex imaginary world.He has maps, transportation systems, characters and equipment. It is often tough to keep track of. DS will often have the characters in groups of 3, so DH and I are assigned a role (he's an only). Sometimes I forget who goes with who, there are dogs, superheros, scary superheros, bugs, weather controllers, body parts, etc. Always in groups of 3. For DS its mostly inside but every once in awhile its outside too - which can be strange when he calls me Leslie (Mr. Big's sidekick from wordgirl, he often takes characters and makes a whole new storyline or expands on what he saw or read) but its usually when the two of us are walking or on line at a store. I have never minded that but pretty early on he knew he was making everything up and started to revel in his imaginary worlds.
What concerned us was that he created elaborate imaginary worlds to deal with his age-mates in school. When the other kids were playing tag, his team of villains was trying to "get" these two girls and guy who had excluded him from their play. We got concerned about how elaborate the scenarios were, how focused they were on the other kids, and how oblivious his "friends" were to what he was doing. They would listen to some of it, they enjoyed some of his storytelling but often it was too much and it was clear there was no give and take of make believe. So we have had to stress that its just pretend and he can't do any of it in real life. He got somewhat annoyed at that. I think it was his coping mechanism for an ill fitting pre-k. We actually talked to him about not doing "the game" at camp and his new K school.
But on the whole, I love his world and don't suppress it at all. We save all the drawings and have tried to keep track of all the character combinations. We have cut it off at the dinner table or out in public but only if its inappropriate to the setting or he is using to try to control the conversation (like when DH and I are talking to each other).
DeHe