At the end of GOF only a handful of people even know that Sirius is an animagus, let alone his loveable big doggie form. But by the beginning of OOTP we have Lucius Malfoy able to "recognize" Sirius by seeing the large black dog with Harry. So we're left with a good mystery.
Harry had been working on his Patronus charm, though, and Malfoy & Co. got what was coming to them. One of the most notable Malfoy moments is where he hints that he knows all about Sirius Black (7.1. 48).
He probably did suspect it. In fact I think early in the book Harry mentions to Lupin that he has had an encounter with the Grim - a big, shaggy, black dog. So Lupin almost certainly knows that Sirius is using his animagus for to stay out of sight, if not to break out of Azkaban or into Hogwarts.
Lucius Malfoy most likely knew Sirius Black was innocent. Lucius Malfoy was one of Voldemort's closest followers in the first war, one of only three Death Eaters entrusted with the protection of one of Voldemort's Horcruxes.
“Technically, it's a ferret.” Barty Crouch Jr. may have been completely wrong to transfigure Draco as a punishment, but he was within the same family of what I believe Draco's Animagus form would take, which is the stoat, or ermine.
“A creature I wouldn't want to kiss . . . a spider!” Harry figures out the riddle, and realizes that a spider is about to attack. But what he doesn't realize is what I now believe: that the spider in the maze is Professor Snape, in his Animagus form. It is Spider/Snape who bears down on Cedric and Harry.
Strikingly, Harry's Patronus was a stag and his mother Lily's was a doe, a female deer, showing that the family's characters were in harmony and formed part of the same animal group.
She was remorseless and was cackling in glee after she had murdered Sirius. Bellatrix couldn't stop raving about it and showed it by singing “I killed Sirius Black” multiple times.
Draco's refusal to reveal Harry's identity to Bellatrix was not because he liked him. It was because he believed that Harry was the only chance they had at defeating Voldemort. At first, Draco admired and revered Voldemort until he threatened his family's safety.
The answer is that Sirius wanted to deflect attention from the real Secret-Keeper. He probably hoped Voldemort would go after him so he could steer attention away from Pettigrew.
He didn't mention that Sirius was an Animagus to Dumbledore because he didn't want to admit to breaking his trust while at school. All in all, Remus did the most to help Harry and the wizarding world.
Draco Malfoy's mother Narcissa was cold, cunning and devoted to the Dark Lord. But she was also a mother, which meant she was willing to risk everything to make sure her son was safe. When Harry survived Voldemort's Killing Curse for the second time, Narcissa pretended he was dead so she could get to Draco.
Draco Malfoy
Malfoy's mother Narcissa might have been one of the few Black family members to avoid being named for a star, but she returned to the tradition when naming her own and only child. Draco's name comes from the Latin for dragon, and Draco is also another constellation named by astronomer Ptolemy.
Sirius's early life proved unhappy; he had come to hate most of his relatives, in particular his mother. He rejected his family's pure-blood elitism and reverence for the Dark Arts. At Hogwarts, rather than be sorted into Slytherin like the rest of his family, Sirius was placed in Gryffindor.
She asked him because if Draco was still alive, she had something to fight for. She had a reason to lie to Voldemort. If Draco is alive, she needs to get into the school to see him and protect him, and helping Harry feign death was the easiest way to do that. But if Draco was already dead, she wouldn't have bothered.
Narcissa's greatest moment, however, was when she chose to betray Voldemort in Harry Potter and the Deathly Hallows. Not knowing whether Draco was alive or dead, Narcissa chose to lie to the Dark Lord rather than risk losing her son.
Voldemort intentionally made six Horcruxes, but when he used Avada Kedavra on Harry, he unintentionally created a seventh Horcrux. Instead of dying, Lily's love for Harry created a counter 'curse' known as Sacrificial Protection and saved Harry.
Harry Potter and the Deathly Hallows
In this book, Rowling reveals that Bellatrix is the guardian of Helga Hufflepuff's cup (though she is unaware that it is a Horcrux), which Voldemort has entrusted the Lestranges to keep in their Gringotts vault.
In Deathly Hallows, Hermione faced a real test of her physical and psychological stamina. After being on the run from a bunch of Snatchers, the gang were taken to Malfoy Manor, where Bellatrix proceeded to torture Hermione using the Cruciatus Curse.
"Why didn't you tell her? Bellatrix?" asked Harry, "You knew it was me. You didn't say anything. " Because Draco knew Bellatrix would called the dark lord, and dark lord would killed Harry Potter and his friends, and Draco is not as bad as his family.
He did not react like that because he feared he was losing the war. He would not rely on Bella, just one mortal, to win him the war. He was too arrogant.
Repeated use of the Cruciatus Curse is torture and Bellatrix Lestrange subjected the Longbottoms to such extremes of pain that it sent them insane.
They are James Potter, Sirius, Wormtail, Skeeter, McGonagall, Talbott Winger, and an unnamed witch who can turn into a cat. The fact that there are so few Animagi just causes us fans to want to know more about them.
Animagus. Lily's animagus form is a Doe, coupling with her husband, James Potter who is a Stag.
Peter Pettigrew's Animagus form was a rat. Colloquially, a "rat" is a snitch or informant. Webster's also lists the following possible definition: "a contemptible person: such as... one who betrays or deserts friends or associates."