My imaginary (well, so everyone else said) friend was called Betty. Betty did lots of things, but I often got into trouble for it even though I told Mum & Dad that "Betty did it!".I can't say for sure what the explanation is, but I am psychic, and I seriously suspect that she wasn't just in my imagination.
I dreamt about her once when I was in my 20's and she was dressed in a pinafore of the fashion close to the turn of the century (1900's) and our house was furnished and painted in the style of that era as well - which is when it was built. So, I lean more and more towards the belief that there was someone there, although in spirit rather than flesh.
I am not quite sure when Betty arrived, but I think that it was when my sister went to school and I was left at home. My sister and I are less than a year apart in age and were inseparable, and more like twins.
One of my favourite films is Frop Dead Fred, partly because it is really funny, partly because it has a serious psychological side to it, but mostly because it deals with imaginary friends in a nice way.
Helen