As with most adaptations from page to screen, the famous eight-movie Harry Potter series misses out on some fan-favorite moments from the books. Though this is an unfortunate reality, it happens with so many movies adapted from books because to write a verbatim interpretation of the book would produce a movie that lasts far too long for audiences.
Though writers are now creating miniseries or television adaptations to avoid this problem, sadly, Harry Potter had no such luck. In the case of Sirius Black, much is forgotten, and much is even deliberately changed to fit the new story, often to Sirius’ loss.
His Age
Any fan of the Harry Potter franchise who’s worth their salt knows about the Marauders. James Potter (Harry’s father), Sirius Black, Remus Lupin, and Peter Pettigrew were four best friends from the generation before Harry. James is twenty years old when Harry is born, as is Sirius (he turns twenty-one the November after Harry was born), which means Sirius would only be thirty-three years old when he first meets Harry in Harry Potter and the Prisoner of Azkaban. However, in order to cast Gary Oldman, Sirius was aged up until possibly his late forties.
Amount of Screen Time
If Sirius Black got the same amount of time on the screen as he got on the page, Gary Oldman would be in every scene of every Harry Potter movie just to accommodate the sheer amount of space Sirius takes up. He deserves that much space, too; he’s one of the most dynamic characters in the story, and one of the most important to Harry. This is clear with the amount of time they spend together in the book, but it’s impossible to tell that from how infrequently Sirius appears in the movies.
Moony, Wormtail, Padfoot, and Prongs
In the original book, Harry Potter and the Prisoner of Azkaban, Sirius Black lays out the entire story of the Marauders and the Marauders’ Map for Harry, Ron Weasley, and Hermione Granger. Sirius Black and his best (and last) remaining friend, Remus Lupin (fellow Marauder), tell the entire tale of how Remus is a werewolf, Sirius, James, and Peter became Animagi, and they created the Marauders’ Map, as well as turned the Shrieking Shack into the location of legend it has since become.
This is all completely removed from the movies; they didn’t even film a scene discussing the Marauders creating the Map. Instead, all we get is a bunch of clips in Harry Potter and the Half-Blood Prince of James bullying Snape for the Snape sympathizers out there.
Appearing at Hogwarts
In the movies, Sirius tries to give Hogwarts School of Witchcraft and Wizardry as wide a berth as he can, while he can, which makes sense—he’s on the run, and he’ll be thrown in Azkaban (or, worse, killed) if he’s caught. Because of that, Harry only sees the shape of the Grim in the clouds while he’s playing Quidditch.
This isn’t how it originally happened in the book, though. Instead, in the book, Sirius attends Harry’s Quidditch game in his Animagus form as Padfoot, a huge black dog, so he can watch his godson play. Another missed opportunity from the filmmakers.
Friendship with Crookshanks
If someone made a Venn diagram of disappointment with “cat people” on one side and “Harry Potter fans” on the other, the center where they overlap would be labeled “Crookshanks.” What a waste of a perfectly good cat!
Crookshanks is an exciting and dynamic pet character in the books, a character with real personality and intelligence. Sirius even befriends Crookshanks and comments to Hermione just how smart the cat is. However, Sirius and Crookshanks get none of this comradery in the movies.
Relationship to Remus Lupin
A blood-boiling omission from the Harry Potter movies is the complete lack of a strong dynamic between Sirius Black and Remus Lupin. Two best friends who have lost everything, coming back together after years of misunderstandings between them, finally finding a liferaft on the dark ocean that their horrifying lives have become—the story practically writes itself. They even move in together and give Harry joint Christmas presents. They form a small unit of semi-fatherhood to help raise Harry. Did any of this make it to the movie, though? Of course not.
“Nice one, James!”
In the film adaptation of Harry Potter and the Order of the Phoenix, while Harry Potter and Sirius Black are fighting Death Eaters together in the Department of Mysteries, Harry makes a particularly good shot with a spell, and Sirius calls to him, “nice one, James!” Harry looks back to him, confused. This is meant to show that Sirius confuses Harry and James and that he doesn’t know how to separate them.
In the books, though, the real Sirius Black sees Harry as an equal and as a friend, rather than as an adult. It’s this that prompts Molly to remind Sirius that Harry is not James in the books, nothing more. Though this does show how immature Sirius can be, it’s far from implying that Sirius simply sees Harry as James 2.0.
His Maturity Level
Speaking of Sirius’ maturity level, this fluctuates wildly between the books and the movies. In the movies, Sirius looks like a man in his late 40s/early 50s, and he, for the most part, acts like a man in his late 40s/early 50s. Sometimes he’s shown to be reckless, or exuberant, or—well, reckless. They seem to just think, Sirius Black = reckless, and think that’s enough character work.
In the books, though, Sirius has the body of a 33-year-old man and the mind of a 21-year-old guy. He wants Harry to be his friend and often is not the greatest role model because of that. It’s not always positive, but it’s complex and interesting and completely changed for the movies.
Relationship to Harry Potter
In changing his maturity level, his relationship to Harry Potter himself, by default, has to change. Though Sirius’ role in Harry’s life in the books is a very complicated one, it’s also very clear and very warm. Sirius adores Harry and sees himself as, if not a father, something of an older brother to him.
They spent a lot of time together and get along fairly well. In the books, Harry has a strange relationship with Sirius—they don’t seem to know each other very well or spend much time together, but he’s still distraught to lose him. It’s not nearly as fleshed out as a relationship in the movies as it is in the books.
His Death
There are spoilers ahead for a movie that’s been out for years and the book it’s based on that’s been out for even longer, so, if you keep reading at this point, that’s on you.
Sirius Black’s death is changed in a massive way from page to screen. In the book, Sirius gets knocked through the Veil between life and death by a spell from his cousin, Bellatrix Lestrange, which effectively kills him. In the movie, Bellatrix performs the killing curse, Avada Kedavra, on Sirius, and so he’s dead before he even falls through the veil.
Having Bellatrix purposefully murder Sirius in front of Harry in such an irrevocable way, rather than having Sirius’ death be a series of unfortunate mistakes and coincidences that Harry is incapable of stopping, not only changes the death scene itself, but also the impact and consequences of his death further along in the story. Much like the butterfly effect, Sirius’ death changing has lasting impacts on the way the rest of the story is going to unfold.