The actress, who plays Marnie on the hit HBO sitcom, told Company that it was the best ever job, adding that she would still be excited about the show if she was not in it.
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"There is nothing alienating or too hipster about it," Williams said of the comedy's success.
"We're not dating handsome boys, they're weird. We don't have jobs you dream about, in fact, not all of us have jobs.
"It feels accessible. And the relationship between the girls is brilliant. It's like a digital time capsule - people will watch it in 20 years' time and it will sum up a certain generation."
Asked about her character's 'toilet scene', she added: "There were moments reading the script that I thought, 'WOW, okay!' That scene in the toilet was the first time viewers met the real Marnie.
"It's the most private thing anyone can do, but being an actress can make you feel vulnerable. But of course, my grandparents watch the show.
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"I don't know why I was so concerned though, they have been alive for virtually 90 years, so who am I to presume that sex never existed before me?"
Of rumours linking her to the Fifty Shades of Grey movie, Williams said: "That's so funny, I read that rumour too.
"It's certainly nothing that I know of. I did read the first book proudly though, with the cover showing on the subway and everything."
The full interview with Allison Williams can be read in the February issue of Company magazine.
Behind-the-scenes footage of the cover can be viewed at the Company website.
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