My DS 4.5 also is a continuous talker, also with the imaginative stories. I thought we were the omly ones who had to be characters. It's 3 of us, so it's always in groups of 3. And he also takes in information from everywhere and then makes stories up about them, lately in reposnse to a timeline of eras he has decided we are saber tooth tiger (him delightfully pronounced swaber) I got to be the woolly mammoth and DH was t-Rex after a time travel device was created to bring trex into our time period!! DS is learning about audience, he used to not stop talking when I would buckle him in and then close the car door, I admit I paused before opening my door occasionally and could see his mouth moving, now he pauses and just starts right back up once I open the door. He is okay with minimal input when walking or driving, the occasional related question or comment is fine, and now he wants to tell his stories to himself, he will go into his room, not now mommy I am by,myself to tell my stories. The first time he closed his door on my dh, it was a little insulting till we realized it was freeing. But I don't cut him off because one of my clearest early memories is a parent saying to me, honey, you've talked for x minutes straight now you need to be quiet for X minutes. I was so insulted, but I can't say I have never tuned out and I have been caught too - mommy how was my black hole traveling around the sun, what, what???

DeHe