Harry Potter & James Potter: Stag
The moving scene when Harry thinks James has saved him in ThePrisoner of Azkaban will always be one of the saddest moments of the early #HarryPotter movies. It is the first time the intimate nature of a Patronus is revealed, and gives us further insight into the complex characters of the HP universe. The stag represents leadership, strength, nobility and pride.
Ron Weasley: Jack Russell Terrier
Unsurprisingly Ron's Patronus was Jack Russell, a dog that's both loyal and playful. Jack Russel's are also known for chasing otters...
Hermione Granger: Otter
Hermione's is an otter. The otter is part of the Weasel family, which could mean she belongs with the Weasley's. It may also symbolize her future with Ron.
Ginny Weasley: Horse
Ginny's Patronus matches her character — free-spirited and strong. The horse and the stag are also similar in stature, which could link her Patronus to Harry's.
Luna Lovegood: Hare
If you've ever read Alice in Wonderland, you know may know the phrase "mad as a March hare" — this may attribute to Luna's cooky character and why her Partonus is a playful hare.
Albus Dumbledore: Phoenix
Of course, Dumbledore's was an almighty Phoenix, likely thanks to his close bond with Fawkes. Phoenix's are (sadly) fictional, but from what we know about them, they are beautiful, brave and can live for hundreds, if not thousands, of years.
Lily Potter & Severus Snape: Doe
This is the most tragic of all the Patronus' in the series — Lily Potter's was a Doe, the female Deer to James' Stag. However, Lily was Snape's happiest memory, which meant that they shared the same Patronus.
Remus Lupin & Nympadora Tonks: Wolf
For many in the Harry Potter series, love is the happiest memory, so it makes sense that the stories' soulmates would share the same Patronus. Tonks's love for Lupin meant her Patronus was a wolf, before Lupin it was a Jack Rabbit.
Arthur Weasley: Weasel
While the weasel does not match Mr. Weasley's personality, it is connected to the Weasley name.
Kingsley Shacklebolt: Lynx
Kingsley's lynx reflects his calm and reflective personality, but is not afraid to fight for what he believes in when provoked. Lynx's are noble and hunt in high places — Kingsley is the highest ranking Auror and later, Minister for Magic.
Dolores Umbridge & Minerva McGonagall: Cat
Both McGonagall and Umbridge have a cat. In the first Harry Potter book, McGonagall uses transfiguration to become a tabby, and Umbridge is later revealed to be totally obsessed with the furry creatures. It shows the variety of ways the same Partonuses can reflect the personalities and desires. Umbridge is just evil, deceptive and dangerous, while McGonagall is stern, caring and intelligent.
Sirius Black: Big Black Dog
Sirius is the name of the Dog Star, which is the brightest star in the sky. He is also loyal, energetic and brave. The dog also looks like the Grim, which is a nod to his perceived bad boy image.
Seamus Finnigan: Fox
In many cultures Fox's are associated with fire. Seamus has a tendency to blow things up.
Cho Chang: Swan
Like #JKRowling, Cho Chang is the graceful swan. They are very beautiful, but tend to live a solitary existence.
Aberforth Dumbledore: Goat
Aberforth's fondest memory is feeding the goats with his sister Arianna, so it makes sense that his Patronus is a goat. On the other hand, there have been some unsavory rumors that Aberforth's love for goats is a little more... intimate than most.
The nature of a Patronus says a lot about the caster, which is why Pottermore's attempt to recreate this process was both brilliant and frustrating. It didn't offer much explanation for its choice, meaning you probably need to figure it out for yourself — sorry Mongrel dog.