When it comes to films, the likes of Belle de Jour and Love Story have long been the default fashion classics. But the people name-checking those movies have obviously not seen Clueless. For a generation raised in the 90s, and another one just referencing it, the high school comedy – which came out in 1995 – is the one. It comes with meme-able lines (“Ugh, as if!”, “You’re a virgin who can’t drive”), a cast of characters including Alicia Silverstone’s Cher, Stacey Dash’s Dionne and Brittany Murphy’s Tai, and a wardrobe that stands up to multiple viewings. Here, Mona May, the costume designer behind all of these looks, as well as those for Romy and Michele’s High School Reunion and Never Been Kissed, reminiscences on 25 years of Clueless.

Costume changes were key

The sheer number of outfits is partly behind Clueless’s appeal to a fashion-inclined audience. “Maybe I would say 25 [changes] would be an average [in a film],” May says. She points out that in Clueless, Cher had 60 outfit changes, Dionne had 45, Tai had 30 and Amber (Elisa Donovan) “our fashion victim, she had so many changes. Plus I had to dress all the extras.” It was a learning curve for Silverstone, a teenager with little previous acting experience. “She was a hippie girl, an activist already, fighting for the animals, saving the world in her sweats … She was like, ‘More clothes? More fittings?’ Years later we talk about it, we are still friends.”

Every film starts with a mood board

May says that, with Clueless, it was about the group of characters. “Cher, she is the leader, she is the queen of the school in a way. She’s very put together, she’s tailored,” May says. “Dionne has more experience with boys, she’s a little sexier. Her clothes are a bit shorter and risqué maybe. Then you have Tai. It’s a beautiful journey of hers where she finds out who she is. She kind of takes that Cher persona in a way, she wants to be her, but then she finds out, ‘Maybe this is not really me.’ [At the end] she’s dating the skateboarder, she’s got the skateboard.”

Grunge was the enemy

“When we went scouting on the film to high schools, it was Kurt Cobain, it was Nirvana, girls were looking like boys, it was baggy shirts, baggy pants,” says May. Instead, collaborating closely with Amy Heckerling, Clueless’s director, May created a look that was inspired by the idea of teenage girls shopping when money is no object. “These girls had so much money they could probably go to the [fashion] shows and pick their favourite things,” she says. “All the information from the runways really transmuted through the prism of high school. It had to become real. Because, otherwise, they’re just snooty models running around in high heels.”

‘High low’ was a new concept for fashion in the 90s

“I did thrifting, I did mall clothes, I did a little bit of designer and I mixed it together,” says May. “Nobody wore high and low. Dionne had a D&G [Dolce & Gabbana’s cheaper line] top, but then she had a 50s purse. I think that was really fresh.”

Azzedine Alaïa was essential

The scene in which Cher gets mugged while wearing her red dress by “totally important designer” Alaïa is a fan favourite, thanks to the much-quoted conversation between the teenager and her mugger: “This is an Alaïa” she trembles. “An a-what-a?” he responds. The dress in question was the result of May’s hard work – Alaïa was not a household name in America at the time. “I reached out to Alaïa’s group and said we just think this dress would be perfect for our main character,” she says. “I had to kind of confess that the dress would be on the ground. [But] they were so great. They did send us the dress.” It is thanks to May that Alaïa is in the script at all. “That’s why working with Amy is so incredibly cool,” she says. “I was able to find a dress and she changed the line.”

Fit was everything

May says she altered everything to fit the actors exactly, a trick she has continued to use throughout her career. “It could be Nicole Kidman, Jennifer Aniston,” she says. “I’ve done so many films with Drew Barrymore, someone that really trusts me to dress her and she doesn’t have the body of a young girl that’s size zero, which is wonderful.” May says that, on Clueless, fit helped with character, too. “It’s that half an inch [shorter skirt] on Dionne that made her a little bit more risqué.”

Cher’s plaid yellow suit was almost blue

The much-referenced skirt suit that Cher wears at the start of Clueless has inspired designers such as Henry Holland, as well as endless Halloween outfits. It was sourced from D&G and May had options in blue and red, too. “This was the opening of the movie, in the quad,” says May. “We tried a blue suit, which was just great with the blond hair. We tried a red suit, which was a little bit trying too hard. And when she put the yellow one on, it was like, ‘Yes!” That yellow was like a ray of sunshine, like she was the queen. So we knew that in that scene when she’s walking through, she’s going to radiate, this is all you’re going to see.” The fabric is why this outfit remains a favourite, according to May. “I mean, who doesn’t like a plaid? It’s fabulous.”

The camera loved the Clueless look

“The director of photography, Bill Pope, was a brilliant film-maker,” says May. “The way that he looked with his camera, it was like an eye of a fashion person. He would go up the leg of Cher so you would see them walking. It’s almost like a runway in the sense that you really got to see the details.”

Clueless is available to watch on Now TV