This is one of my favorite pets because when I got it - I didn't know he was a Rainbow Mane, or just how valuable a pet he was considered to be. I recall watching him grow (not quite understanding how the stages worked), each time thinking 'Yay! I got the *color* one' (except when he turned Pink, then I was sad) .
By the time he returned back to the rainbow foal, I was depressed going 'Aw man, I got the PPS form' (Note: There's no PPS Rainbow Mane, I have no idea why I thought there was XD). But then he turned into the beautiful stallion he is now, and stole my heart, and I was over the moon once I learned how special he really was.