First introduced in Harry Potter and the Prisoner of Azkaban, the Patronus is an advanced defense charm. It’s used in the series as a shield to protect wizards from dementors. A Patronus is produced by concentrating on happy memories, and it can take on two forms: corporeal and non-corporeal.

The non-corporeal form of a Patronus looks “like a wisp of silvery gas”, while the corporeal form of a Patronus takes on a shape that is unique to each wizard. Throughout the Harry Potter series, we get to see a lot of Patronuses, including but not limited to Harry’s stag, Dumbledore’s phoenix, and Snape’s doe.

But can you choose the shape your corporeal Patronus takes?

The easy answer to that question is no. And the hard answer is yes and no.

So here comes the easy answer. The Patronus charm is a very difficult spell. As Professor Remus Lupin puts it in Prisoner of Azkaban:

“The spell I am going to try and teach you is highly advanced magic, Harry – well beyond Ordinary Wizarding Level.”

Harry Potter and the Prisoner of Azkaban, Page 237

Harry spends a great deal of his third year just learning how to produce a Patronus charm, and he teaches Dumbledore’s Army to use the charm in Order of the Phoenix.

The fact that a wizard can produce a Patronus at all is an indicator of great skill. The vast majority of wizards who use the spell will never be able to change the shape of the Patronus – it is much too difficult.

And here comes the hard answer. Sometimes, the shape of a wizard’s Patronus can change. This is the case for Nymphadora Tonks.

In Half Blood Prince, Harry says that Tonks’ Patronus has changed shape: into that of a wolf.

“Tonks’s Patronus has changed its form,” he told him. “Snape said so, anyway. I didn’t know that could happen. Why would your Patronus change?”

Lupin took his time chewing his turkey and swallowing before saying slowly, “Sometimes … a great shock … an emotional upheaval …”

“It looked big, and it had four legs,” said Harry, struck by a sudden thought and lowering his voice. “Hey … it couldn’t be –?”

Harry Potter and the Half Blood Prince, Page 340

Throughout the course of the book, we learn that Tonks has fallen in love with Lupin. However, in Half Blood Prince, the two are separated – Lupin is living with werewolves and involved in dangerous missions, and Tonks is sort of cut off from the rest of the Order of the Phoenix.

Also, she’s trying to get Lupin to understand that she doesn’t care that he’s a werewolf – she’s still in love with him and nothing is going to change that. It’s the combination of all of this that causes the “emotional upheaval” that Lupin is talking about it – and it’s this that causes Tonks’ Patronus to change shape.

However, in this case, Tonks isn’t necessarily choosing the shape her Patronus now takes on – this is an outgrowth of what’s going on inside of her.

Lastly, we turn to J.K. Rowling herself: on Pottermore, she quotes “the great eighteenth-century researcher of Charms, Professor Catullus Spangle”. He says that sometimes, a wizard’s Patronus can be the same shape as their favorite animal. However, this occurrence is neither common nor to be overlooked.

“Whatever the form of their Patronus, you would be well-advised to show respect, and occasionally caution, towards a witch or wizard who produces the Patronus of their choice.”

Patronus Charm“, J.K. Rowling

So there you have it. Patronuses are tricky business and choosing the shape of your Patronus is even trickier. Sometimes, in the case of great emotional stress, your Patronus might change. However, when you’re up against a Dementor, it doesn’t matter what it looks like, so long as it protects you.

While you may not be able to choose your Patronus, here in the real world, you can find out what it could look like. Just visit Pottermore (or click on this link) and when you find out what it is, comment below.