This is what i think would have happened if Sirius had left a letter for Harry. Review much appreciated! :D
Dear Harry,
If you're reading this, then it sucks 'cause that means I'm dead. But I knew I had to write this. There are just a few things I never got a chance to tell you.
When I first saw you after Azkaban, I thought you were James. I swear, I nearly turned back into myself to talk about the latest Quidditch match. Until I saw the Lily in you. Bottle green eyes. I know you hear this way to much, but you are exactly like James, except for Lily's eyes.
You parents never deserved what they got. They were killed on a mere whim you would be the one from the prophecy. Your whole childhood was ruined, taken away from you in an instant. When I saw the wreckage your house was in, I thought there was no way you would be alive. But you were. It was a miracle. When Hagrid wouldn't give you to me, I knew I had two options. One, throw myself of the nearest cliff, or Two, kill Peter Pettigrew. I figured I'd kill the rat then go look for a cliff. You know, James was the only one who really liked Pettigrew. Remus and me weren't all that keen on him at first, but your father insisted we give him a chance. Said we shouldn't judge him before we knew him. You were right when you said that Prongs wouldn't have wanted us to kill him. When I found Wormtail, he knew what I would do. So he attempted to kill me first. He was never really good at magic and he missed. A few muggles had seen the light and come to their windows. That's when he yelled that I had betrayed James and Lily, cut his finger off, and blew up the street. You might have heard that when the Ministry got there I was laughing. I was laughing at the fact Moony had might be part physic. He said to me one time, "Padfoot, we need to help him with his animagus potion. If he tries to do something, he could blow apart the street!". I never thought Moony was the divination sort. And that was the only thing that stopped me from killing myself that moment. That, and the vow that one day Wormtail will be killed by me, or a person who looks a heck of a lot like me.
At school, Lily and James getting together didn't go as smoothly as James had planned it. Prongs made one of the biggest mistakes you could make with Lily; hurting her friends. She was like James in that way. I suppose, I kinda had a crush on your mum when I met her. She was the prettiest girl in the grade. But when James be talking with Lily, there was a sparkle in his eyes, even if they were arguing and yelling words you shouldn't use. You knew not to get in the way of him and his Lily-flower. I think he shoved Amos Diggory into the vanishing cabinet when he heard that he had flirted with her. They didn't find him for a week. James never gave up though. Not even when a prank went wrong and a bucket of toadspawn got glued to Lily's head. She was yelling abuse at him for what seemed like weeks. Understandable of course, since the bucket took 4 hours to unglue. But when Lily's parents, your grandparents, were killed, James found her and comforted her. I think she realised he had grown up a bit, and they started going out. On their wedding day, I don't think either of them stopped smiling all day. They just glowed. I've only once seen them happier.
It was quite a fiasco when you were being born. Moony and I were in the room outside and all you could here was Lily yelling for the healers to give her her wand back so she could curse James. She almost broke his hand. After about 16 hours of abuse, your dad came out. His eyes were so bright they were almost glowing. There was so much pride and joy in his face when he told us it was a boy, and you had been named Harry James Potter. We saw you and fell in love with you as well. You were so cute as a baby. You had a tiny tuft of black hair on your head.
I actually bought you your first broomstick. It was for your first birthday, and it would hover about 2 feet off the ground. You parents were in hiding then, and I was doing order work, so I couldn't see them in person. But you mum did send me a picture. You almost killed the cat. I think Teazle was crushed when the house collapsed.
There are many things i admire about you Harry. Your goodness of heart, your love of your friends, your talent on the Quidditch pitch. You would help absolutely anyone. I know your father would be just as proud as I am of the man you're becoming.
I've never forgiven myself for James and Lily's death. I killed them, no matter what other people think. But I have a feeling that if you're reading this, I didn't die from spattergroit. I just hope I died fighting. If I did, then I died for Lily. I died for James. I died for you. Tell Remus he's one of the most loyal friends a guys could have. Tell him as he's the last true Marauder, he had better keep up the pranking. Tell him I'm sorry for doubting him, and that I love him. And you, Harry, keep on fighting. You will defeat Lord Mouldybutt I know you will. Your spirit is strong and your heart is good. Just keep Ron and Hermione with you. I don't know if you're like this, but if things get hard, James would usually push us away. They love you and will always be there for you; The Golden Trio. Not as good as the Marauders, but it's as good as you'll get. You're your mother and father through and through Harry.
I love you.
Your Godfather,
Sirius
What do you think. Should i leave it as a one-shot or make more chapters? R&R