well I didn't have an imaginary friend, but my older sister would pretend to be someone else.. she was deadly serious about it, so I had to call her by that name and everything.. I actually really liked this other person.
Her name was 'Hearty the snail' Her dad was gus and they sometimes delivered batnail pizza.
We had a full on story about her and everything. I used to love it, my sister bought a chocolate heart at the supermarket once and I never saw her do it, and later, 'hearty' gave it to me as a present. I used to love it.