When my brother who was closest in age to me stared school, and I was left at home with my home-body mother and baby brother, (I was around age 4) I invented "Lynnette", a derivative of my own name. We lived then in a rural area, and I apparently was bored, in that my 5 older siblings were all off in school all day long.
Knowing full well that Lynnette was imaginary, I'd insist that she also be given a cooky whenever I got one, and so forth. Lynnette came in handy to blame for things, like once when I cut my bangs off to the quick, (No one had ever told me NOT to (!), so it wasn't really being naughty; in fact I didn't get into real trouble for this-- it's just that they have to grow back and the process looks kinda wierd).
In later years I've seen a few t.v. shows about multiple personalities, and now I wonder about the fine line between split personalities and invented imaginary friends, like mine....
A childhood belief about imaginary friends

others believed things like this
- i thought split personalities were like having dreams. the dreams i had were all my personalities!— Odd Dreamer
- My older brother used to tell me if you ate raw potatoes your teeth would grow long and curly!— Lauren
- My Mum told me she invented skipping and I believed her and told all my friends - still living that one downAnon
- My brother was terrorised by an imaginary charecter called anorak doo-dah— Corin
- I used to belief sloths lived in trees outside my childhood home. My older sister told me so.Anon
- When I was in elementary school I use to think that teacher lived at school at their desks all year long.Anon