The producers had told her that she didn’t have to do anything she wasn’t comfortable doing. She told them she didn’t want to sing or dance (which has been the salvation for female guest hosts like Catherine Zeta-Jones, Anne Hathaway and Scarlett Johansson), and the writers of her opening monologue were having trouble coming up with a premise that pleased her. “There’s one specific pitch that we can’t do,” Fox said. ‘They wanted me to do a Q. and A. with the audience for the opening monologue. And Hitler is in the audience. Hitler stands up and says, ‘Why did you compare me to Michael Bay?’ ” Fox laughed. “Which is funny, but we can’t do that.”

Giving hope to men everywhere, Fox told Cosmopolitan magazine that her ideal date would be “a sexy sandwich” with Andy Samberg and the roly-poly comedian Jonah Hill, so Samberg thought about recreating that image for the monologue. That idea was also nixed. It was the day before the show, and the monologue still wasn’t written. On the set, Fox, in her usual uniform of leggings, low-cut T-shirt and long cardigan, was practicing her lines, which were in Russian. In a strange way, “S.N.L.,” which required her to play seven different characters, was more acting than Fox has done in her entire career. “I’m not one of these people who grew up studying acting or went to theater school,” Fox told me at the hotel. “I don’t know if I’m talented, I don’t know what I can do or can’t do. I had no skills at all. As a child, I had it in my head that I was supposed to be doing this, and then I did it. But I didn’t know what I was doing.”

Fox was born in Oak Ridge, Tenn. Her mom, who Fox claims looks exactly like her, separated from her father, who was a parole officer, when she was 3 and eventually divorced him. She then married a much older man, who moved the family to Port St. Lucie, Fla. Fox’s stepfather was very strict. He was religious, and Fox grew up Pentecostal and attended a Christian high school. “I was always alone,” she recalled. “I withdrew. But I wanted to be an actress from the time I was 2. My mom said it was the only thing I ever said I wanted to do. When I was 4 or 5, I watched ‘The Wizard of Oz,’ and for a year, I asked her to call me Dorothy. When my mom explained to me that Dorothy was not real, that an actress plays her, I decided I wanted to be an actress.”

She modeled briefly in catalogs, and when she was 15, an agent sent her on an audition to be an extra in “Bad Boys II,” directed by Michael Bay, which was shooting in Florida. “They put me in six-inch heels and a stars-and-stripes bikini,” Fox said. “Sent me to Michael. He approved me. Then they put me in the scene under a waterfall. You got $500 extra if you were willing to get wet, and I was thrilled to get wet. I was still a child, but for those two days I was being treated like a grown woman. I felt like I should be in a bikini dancing under a waterfall: that is where I thought I belonged.”

From an early age, Fox was restless. At 14, she regularly stole her mother’s car and was constantly punished, which only made her more rebellious. “I was always trying to get away,” Fox said. “I hated authority figures telling me what to do. They wanted me to be conservative, but when I was a kid, I was obsessed with looking like Barbie. I was wearing the smallest clothes I could find. My mom wouldn’t let me dye my hair blond, but I used Sun-In, and I had orange hair for two years. What can I say? It was Florida. But my mom was right: being brunette was the one thing that made me memorable. I didn’t look like anybody else. So I clung to that.”

Her first acting role was in “Holiday in the Sun,” an Olsen twins film that went straight to DVD. By 15, she persuaded her mother to take her to Los Angeles for pilot season, where the television networks cast their new shows. At 17, she moved to L.A. and landed the role of Lindsay Lohan’s enemy in Disney’s “Confessions of a Teenage Drama Queen.” “I played the bitch, of course,” Fox recalled. “I was always cast as the bitch. The light-haired girl is the sweet leading lady, and the dark girl is the sexy bitch.” She paused. “I didn’t know how to act when I did that movie. I just mimicked all the bitches I’d seen other people play on TV.”

By 18, Fox was on her own. Her mother went back to Florida, and Fox moved to New York to co-star on “Hope & Faith,” which taped in Queens. The comedy, which ran for three seasons, was about mismatched sisters and was shot in New York to accommodate the schedule of one of its stars, Kelly Ripa. “I had two lines a show,” Fox said, “but I was working, so I was happy.” One week, Brian Austin Green, who was part of the original cast of “Beverly Hills, 90210” (he played David Silver), was scheduled to appear as a guest star. “He played himself,” Fox recalled. “Kelly Ripa’s character was kidnapping him for some crazy reason. I didn’t know who he was from ‘90210,’ but I liked him right away. Everyone was around the monitor watching a scene, and Brian accidentally touched my leg. I remember literal electricity shooting through me and out me from every direction. It was like magic.”