My imaginary friend wasn't human, he was a tiger that would sit by my desk in school and accompany me home. I did find out years later that I'm a tiger in Chinese astrology-- for what it's worth.
I've always felt a strong connection with animals-- one of my earliest memories is of lying in my crib at night, which was against the wall under a window, and I used to be terrified that a big owl would break through the glass and get me. Part of me wonders if I had been a prey animal in a past life. Also when I was around four I used to dream that I was a dog (or wolf?) just walking and walking through snowy fields and forests at night, it was so vivid again I wonder if it had a past life element to it. Who knows....