As Prizoner of Azkaban taught us, there was much more to Scabbers the Rat than meets the eye. Pottermore gives us an in-depth look at the behind-the-scenes work that went into making Peter Pettigrew much more than a rat.

He was once someone James Potter could call ‘friend,’ but that all changed once Lord Voldemort started to have a say in things. Peter Pettigrew, played by actor Timothy Spall in the movies, is one of the franchise’s sneakiest characters. He was the one who betrayed the Potters to the Dark Lord, helping cause an unflinching ripple effect that would set off the events of the entire Potter series.

Pottermore has a behind-the-scenes look at what went into bringing this rat fink character to life.

Sneak and Squeak

Courtesy: Warner Bros.

As we learned, Peter Pettigrew is an animagus, so the film crew had to find a way to make Spall look rat-like in appearance. He was living as Scabbers for more than a decade, so a lot of those rodent qualities had to stick with him.

Prisoner of Azkaban director Alfonso Cuarón wanted to see a character who was delightfully creepy, and someone who really embodied all the qualities of a rat. Not just an animal, but someone who was also a great betrayer. Spall was adorned with giant incisors, long claw-like fingernails, bald patches in his hair and scaly parts of skin. He also wore a high-cuffed coat with lots of fuzzy fabric, and elevated shoes to give him a sneaking sort of gait.

And what did Spall think of the character he so masterfully played for us? “Peter Pettigrew is a very shrewd, cowardly, weak, conniving, audacious, lying little character that is always ready to save his own skin. Apart from that, he’s very nice and rather handsome,” he says.

Sounds about right.

For a full scope of the behind-the-scenes content, plus a five-step evolution process from rat to man, check out the whole article over at Pottermore.