The Fashion supremo, who designed outfits for the band's reunion tour said that the 33-year-old singer "was the most daring".
"She wanted to experiment, to surprise and be different. Her only request was that we give her hips," Cavalli told Grazia magazine.
He said that he had met each one of the Spice Girls personally to know their personality.
"I met each one on their own so I could get an idea of their personality," he said.
"I asked them about their bodies, what they wanted to show and hide, and we talked about how they had evolved in the years since they were Spice Girls," he added.
He also made them view his archives and asked what they wanted to wear.
Geri Halliwell wanted to show off her toned body while new mother Emma Bunton wanted all covered up, he revealed.
"We updated Geri's iconic Union Jack dress into a corseted Swarovski crystal-studded mini dress," he said.
Melanie C wanted to be more rock chick than sporty, he added.
Cavalli further revealed that Mel B was very assertive with the outfits.
"Melanie B, she was very strong, very assertive. Oh my, she was very hard work," he said
"I had to change her outfits twice. She wanted shiny, body-conscious clothes, and animal prints...."he added.