Torturing celebrities, lesson one.

If they’ve ever written and performed the theme to a kids’ cartoon, make ’em sing it. Doesn’t matter if it’s 8 in the morning.

“I’m your basic average girl, and I’m here to save the world.

“You can’t stop me ’cause I’m Kim Poss-i-ble.”

Christina Milian is nothing if not a good sport.

The Jersey City native has two movies out: last weekend’s “Man of the House,” and this weekend’s “Be Cool,” the “Get Shorty” sequel that takes Chili Palmer (John Travolta) from the movie business to the music business, where the joke is not in how easily a mob enforcer can have his way with the insiders but how many of the insiders are just like him.

Milian, 23, is uniquely qualified to play a singer in a movie about the music biz. She’s been on TV and in films since she was 11. She scored two Grammy nominations this year, and she’s had hits with “Whatever U Want” and the “Dip it Low.”

We caught up with her by phone from Miami.

Q: Which is dirtier, the movie business or the music business?

A: Oh, the music business, all the way. That’s why “Be Cool” is so on the mark. When it comes to the music business, there are no rules! Elmore Leonard (who wrote the novel) did his homework. I can definitely say that at one time or other I have met each character in this movie. They just had different names.

Q: So you’ve had trouble with agents, managers, record companies?

Inside jokes overrun ‘Be Cool’ (03-04-05)

A: There are some tough guys in music. Suge Knight (the jailed Death Row Records chief) scares me so bad I have to change the channel, even if I just see him on TV. Guys want you to sign away your life. Just every kind of sleazy person you can imagine works in music. You really need your own Chili Palmer to get you through. Mine was my mom. She’s my manager, and she’s got my back.

Q: Your big break in the movie is an onstage duet with Steven Tyler and Aerosmith. How was that?

A: I was scared of working with a legend like John Travolta, but singing with Aerosmith? Scared to death! We did that, live, in L.A., in front of 30,000 fans there to see an Aerosmith concert.

I love “Crying,” the song we did, and I just didn’t want to mess it up. We did “Crazy,” a couple of songs, shot those songs three times, live. No rehearsals. Just do it, film it, and get out of there.

Q: Anything that the movie taught you about the music biz?

A: Did you see the scene where Cedric and his guys from the Dub MD (a rap group) had the radio-station program director tied up in the back of his car, hitting him with the spatula? I’m gonna make sure I have a spatula with me the next time I try to get a station to give me some airplay!