Neville's Nerdiness Was – Gasp! – Fake, Says Matthew Lewis' 'Harry Potter' Costar

It seems someone might need an extra-strong dose of Veritaserum.

Although Matthew Lewis’ transformation from mild-mannered wizard to muscled Muggle continues to shock the Internet, one of his Harry Potter costars says Lewis – who starred as nerdy Neville Longbottom in all eight Potter films – has been hiding a secret all along.

“Matt Lewis has been a very good-looking guy for a little while now,” Alfred Enoch, 26, who played fellow Gryffindor Dean Thomas, told PEOPLE Monday at Entertainment Weekly and PEOPLE’s Upfronts party in New York City.

“I mean, he had to wear fake teeth, and he had to wear a fat suit,” says Enoch. “They gave him haircuts that he was really upset with. So, that was sort of a ploy to hide his greater beauty from the world.”

Since then, of course, Lewis has amassed his own Neville’s Army of sorts for his dramatic physical transformation, which recently has been on full display on Instagram. His change even led to the phrase “Longbottomed,” which means to suddenly go from Durmstrang cold to dragon-fire hot. (“It kind of leaves me at a loss for words,” Lewis has said of the attention.)

“Like the sun emerges from behind the clouds, I knew it, it wasn’t surprising,” Enoch says of Lewis. “It was just like dressing someone down, and then they start looking a bit cooler. It’s like the teen-movie thing – ‘She couldn’t possibly be the most good-looking person in the film.’ Of course she can – she’s wearing glasses and is a bit artsy!”

Enoch adds with a laugh: “I’m happy. He’s an attractive man and should be celebrated!”

Enoch has moved on, too, of course. The English actor now stars as Wes Gibbins on How to Get Away with Murder, for which he was nominated for an NAACP Image Award for best supporting actor in a drama series.

“For me, it was such a weird experience in the first place because I’ve never worked out here in the States, and it was all a big surprise,” he says of starring on the ABC show. “For it to take off the way it did, that was so far beyond what I was [expecting].”

• Reporting by JEFF NELSON