Breakaway and Alexsmom, so glad to hear this isn't just me - though concerning that perhaps it's not going to go away any time soon! DD4.5 also insists on DH and I doing animal voices, and giving us the script, or us pretending to be animals (in just the right way). And she must have undivided attention seemingly for every hour she is awake.
She also insists that we all take on characters from whatever book or TV show she is obsessed with and is furious if we forget to remain in character (which can change through out the day!).
Unless I am doing chores she is terrible at playing on her own (nothing else is acceptable - if I have to do some work, take a phone call etc, too bad). When she can see that I am physically busy she plays beautifully on her own and often doesn't want to stop - but this seems to be forgotten within minutes of me finishing up.
I can't stand make believe games (making animals talk, pretending to be a horse/dog/cat etc), I wish I could because she really does love them, but I just find them so tedious. DH is much better at them - but is also at work all week so hasn't been subjected to them day after day! I have (rightly or wrongly) explained to her that I think it is fantastic that she has such a wonderful imagination, but that my brain is not so imagination-y. I have said I will play that kind of thing for up to an hour a day (I often do more, but she's pretty good at accepting a time limit), but beyond that she is very welcome to play that kind of thing for as long as she likes while I do x. I explain that I'd rather play a board game, cook with her, read to her or her to me, draw with her, do puzzles etc. I also say that she shouldn't not play with the toys she really wants to just because I am not playing with them because then she misses out. I also do what Greengully suggested and say 'ok, I will do this for 15 minutes, then I am going to do x.' That works ok - but only really well if after the 15 minutes I am... doing chores

More recently I have started explaining that just as there are things that she wants/needs to do there are things DH and I need/want to do and that as a family we have to compromise a bit so that everyone can be more or less accomodated. She is starting to begrudgingly accept this.
Man it can be intense though. I am introverted too, and sometimes the constant talk (all of which requires a response) and her need for stimulation just gets overwhelming. Some times I escape to the study for a few moments to stare out the window for a few minutes - that is until I hear 'mmmuuuuummm, where are you?'
So..still happening at 7 you say. Oh dear!