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Harry Potter and the Prisoner of Azkaban, 2004

 "The eyes behind the glasses were bright green, and on his forehead, clearly visible through his hair, was a thin scar, shaped like a bolt of lightning," described J. K. Rowling in the third book. A now-teenaged Harry battled soul-sucking Dementors (and discovered the identity of the mysterious inmate) in the Alfonso Cuaron-directed installment.

Older and even more brilliant, Hermione got branded "an insufferable know-it-all" by one of her professors. Certainly she was smart enough to ditch her bangs for a more flattering layered cut!  

The "tall and gangling" Hogwarts student added a few inches to his height with a rumpled head of hair 

Harry Potter and the Goblet of Fire, 2005 

For the fourth film, Radcliffe had to bulk up to perform the stunts necessary for the Triwizard Tournament—a fact that was all-too-evident in a fan-favorite shirtless scene. Adding to his teen-dream appearance was a shaggier hairstyle.  

A magical makeover! For the annual Yule Ball (and her date with Viktor Krum), Hermione used her wizarding skills to turn her frizzy waves into elegant spirals. As the book explained, "She confessed to Harry that she had used liberal amounts of Sleakeazy's Hair Potion on it." 

Ron's grown-out locks suited him better than the hand-me-down formal robes (complete with '70s-style ruffled shirt) he would be forced to wear to the Yule Ball.

Harry Potter and the Order of the Phoenix, 2007

Harry grew up with a closely cropped cut and a growth spurt: "He was a skinny, black-haired, bespectacled boy who had the pinched, slightly unhealthy look of someone who has grown a lot in a short space of time." (17-year-old Radcliffe, however, topped out at 5'6".)  

 In the fifth installment of the Potter series, the wavy-haired teenaged witch began to teach her skills to an army of fellow students—and upped the bickering with secret crush Ron Weasley.  

"He seemed to have grown several more inches during their month apart, making him taller and more gangly looking than ever," Rowling wrote of Ron. In keeping with his character, 19-year-old Grint was clearly more man than boy in the fifth film.

Harry Potter and the Half-Blood Prince, 2009

As the Death Eaters grew more powerful, Harry's life took a darker turn that led him away from Hogwarts. Radcliffe, at least, could celebrate the retirement of his character's class robes: "When you're 18, one of the worst things to be wearing while trying to chat up a girl on the set is a school uniform. You look like a kid! You're not going to score dressed like that!"  

Although still enrolled in her final year in school, Hermione took a rare off-campus journey in clothes of her own choosing. As this was the last movie set in Hogwarts, Watson was overjoyed to ditch her uniform at the end of filming: "I was like, 'Burn it!' Oh my God, to be done with those shoes and that uniform—that was an exciting day."  

Ron became an athlete in the sixth installment—bounding into position on the Quidditch field—and his crush on Hermione grew stronger. "There's more for me to do, which I'm really pleased about," Grint told Entertainment Weekly. The actor even made off with some Hogwarts memorabilia during the last flick filmed in the school: "I managed to swipe one of my ties as a souvenir."

Harry Potter and the Deathly Hallows, 2010

In part one of the final Potter installment, Harry is dodging the Death Eaters, causing him to reluctantly lend his face (magically speaking) to a band of supporters. Radcliffe has similar replication problems, due to camera phones. "I don't want to turn up on everybody's bloody Facebook page," he told Entertainment Weekly. "It's around enough, my face."  

For a wedding scene, Watson looked stunning in ruffled Jenny Packham custom design. "She went from a child to a teenager, but all the time kept in mind that she was Hermione," costumer Jany Temime told Fandango. "She never asked me for more glamorous clothes, even when we were doing our cocktail dress." 

Ron took a beating in the first half of the final installment, but Grint took his character's physical struggles (which included filming on cold wet sets) in stride. As he said to EW, "It's a little bit annoying, but...these films have given me opportunities I never would have had, and I kind of got into this flukily, so I'm just grateful to have been a part of it."