The 38-year-old fashion designer reteamed with her Spice Girls bandmates Mel B, Mel C, Emma Bunton and Geri Halliwell earlier this month for the premiere of their new West End show Viva Forever, reported Digital Spy.
Victoria, who is nicknamed Posh, said, "I was called Posh because I liked the nice restaurants, and the nice clothes, and that was my character. I didn't smile, even in those days."
The singer, who has laughed off criticism of her moody demeanour in the past, said, "There was this very strong image.
And I am very much that person, even now. I get ready to go out sometimes and I catch myself in the mirror and I'm like, 'Oh my God, I've turned into that person'."
Recalling the band's heyday, she said, "The things we used to get up to! We had a lot of fun. Even me."
The documentary 'Spice Girls' Story: Viva Forever' will air on ITV1 in the UK on December 24.
Viva Forever is currently running at the Piccadilly Theatre in London.