As Harry Potter grows up, is shunned by the vile Dursleys, and without his parents, James and Lily, there to guide him through life, he fantasizes about a world in which he has a proper guardian. And one arrives during the events of The Prisoner of Azkaban in the shape of Sirius Black. Widely accepted of being a mass-murderer, Harry helps his godfather go on the run, against all odds.
Tragically, however, they never get the life together they both deserve. The movies did a good job of showing Sirius' arc, but not every little detail could make it on to the big screen.
He Nearly Killed Severus Snape
Severus Snape can't resist sticking his nose into other people's business. He does this to Harry on multiple occasions throughout the course of the series, and he also did it during his time at Hogwarts, something that prompts Sirius into taking drastic - and quite frankly, horrible - action.
In their fifth year, Snape is eager to know where Remus Lupin goes every full moon. Sirius lays a trap to make sure Severus catches Lupin while he's in werewolf form, where he'd likely be mauled to death. Fortunately, this fails, with James Potter getting wind of the idea and intervening just in time. A few minutes later and Harry's guardian angel would likely have been Lupin's dinner.
He Deliberately Annoyed His Parents
The Black family, just like the Malfoy's and Lestrange's, are proud pure-bloods. They believe that only magical folk should ever amount to anything in life and that muggle-borns and muggle-sympathizers are what's wrong with the world. Sirius touches on this in The Order of the Phoenix movie but, in The Deathly Hallows book, more details come to light.
Sirius, being against his family's ideology, did everything to enrage them. He draped his room in the red and yellow of Gryffindor house and even had the nerve to clad his room in posters of muggle girls, with the photos not moving. We have to say, we admire his courage. No wonder his mother blasted him off the family tree ...
He Was Originally The Potters' Secret Keeper
For many years, everybody suspected that Sirius had betrayed close friends, Lily and James. It was widely believed that they'd made him their Secret Keeper, only for him to tell Lord Voldemort about their whereabouts, having been a mole inside The Order of the Phoenix the entire time.
What's not revealed in the third movie is that Sirius WAS their Secret Keeper. However, he decided to pass on the responsibility to Peter Pettigrew because he felt he was the most trustworthy of the lot. How wrong he was. And speaking of Peter ...
He Cottoned On To Peter Because Of The Weasleys
Fans of The Prisoner of Azkaban blockbuster get a glimpse of the entire Weasley clan via a Daily Prophet reading. Their faces are splashed across the front page after they win some money and take a cool-looking holiday to Egypt. But this picture has far more significance than merely being used to flesh out the wizarding world.
It's actually how Sirius realizes that Pettigrew is infiltrating the Weasleys by posing as the rat, Scabbers. He notices the creature is missing a toe and, knowing Wormtail had sliced off his own finger shortly before faking his death, he immediately puts two and two together - giving him the courage to break out of Azkaban in the process.
He Escaped By Starving Himself
Before Sirius is successful, nobody has ever escaped Azkaban before. It's a fortress in the middle of nowhere, surrounded by swarms of Dementors that prey on the misery and suffering of others. The third movie of the series doesn't actually explain how Harry's godfather is able to get away - but the book does.
Put simply, he starves himself. He makes sure he's as thin as possible so that, when he transforms into a dog, he's able to slip through the bars. He keeps the Dementors at bay by using his innocence as a happy thought and, consequently, leaves them surprised when he's able to get off the island - surprised and angry too.
He Tried To Take Harry Early
Not much is said about the night when Sirius was sent to Azkaban and it was widely assumed that he murdered Wormtail and 12 innocent muggle bystanders. There's a brief summary in the film, sure, but that's all fans get (and need) to know. The Prisoner of Azkaban novel is different, though, revealing that Sirius tried to take Harry on the night James and Lily were murdered.
After seeing Peter's house is empty, he fears the worst and races to Godric's Hollow. Once there, he insists on taking the Boy Who Lived but, in the end, reluctantly hands him over to Rubeus Hagrid. He even gives the half-giant his old motorbike, an act referenced in The Sorcerer's Stone.
He Was Close To Crookshanks
Crookshanks, the cat, only makes a brief appearance in The Prisoner of Azkaban. That's a shame because, in the source material, the creature has a far bigger part to play.
Sirius actually befriends the cat. Crookshanks assists the escaped convict in trying to get hold of Wormtail and also helps him lie low, pressing the knot on the Whomping Willow to ensure he can hide in the Shrieking Shack. The creature's role should have been more prominent in the film, as fans would have loved to see more.
He Gave Ron A Pet Owl
At the end of the third novel, Ron Weasley is left feeling a bit glum. Though Scabbers actually turned out to be a middle-aged man who would sleep in his dormitory, Ron is disappointed that he'll no longer have a pet around. Harry has Hedwig, Hermione has Crookshanks, but he's left with nobody.
That is until Sirius allows him to keep hold of a crazy, wild little owl named Pigwidgeon. Ron doesn't immediately take to the little furball but, over time, grows fond of him. Pig is never mentioned or seen in the movies and, therefore, only book fans know of his existence.
He Gave Harry His First Broom
In The Deathly Hallows: Part 1 DVD and Blu-Ray, there's a deleted scene. It shows Harry reading a letter found in the bedroom of Number 12 Grimmauld Place, while he, Ron and Hermione are lying low there. The Boy Who Lived then discovers, through its contents, that it was actually Sirius who gave him his first broomstick.
It was a birthday present and Harry, as an excellent Quidditch player in the making, absolutely loves it. This is a flashback that would have been really entertaining for viewers to see but, alas, it wasn't meant to be.
He Didn't Die Via Avada Kedavra
Sirius, devastatingly, is killed off in The Order of the Phoenix movie. This happens via the Killing Curse, with Bellatrix Lestrange striking him in the heart. Things are somewhat similar in the book of the same name but still slightly, and significantly, different.
Sirius is hit with a random curse, not Avada Kedavra, and then tumbles through the veil. Like in the blockbuster, he dies with a smile on his face, yet that doesn't make his passing any easier and it enrages Harry, who then pursues Bellatrix with vigor. Harry's godfather is eventually avenged when Molly Weasley murders the Death Eater in the Deathly Hallows: Part 2.