HOLLYWOOD -- It's frightening how big a role the Scary Movie franchise has played in the careers of Anna Faris and Regina Hall.

Both women were unknown actresses when Keenen Ivory Wayans cast them in 2000 as the heroines of Scary Movie, his outrageous spoof of such youth slasher films as Scream and I Know What You Did Last Summer.

"I'm sure I auditioned 500 times before Keenen cast me, I wasn't a known quantity at the time. I didn't think I'd get the role because I was 29 and he was asking me to play a high school student," says Hall.

Hall, 35, has reprised her character in each of the sequels including Scary Movie 4, which opens tomorrow.

David Zucker took over the director's chair for Scary Movie 3 and again for Scary Movie 4.

"David allowed Brenda to be smarter and she's no longer as loud or unrefined, but she still likes to get it on with as many guys as possible."

For Hall, there was another major change once Zucker took over the franchise.

"Keenen encouraged us to improvise. He's really loose as a director. David choreographs every joke. It's very specific."

Faris explains just how specific Zucker can be. "David even has a list of facial expressions. He tells you which one he wants you to use for a specific moment. David never talks about character. He talks about how we're going to get a laugh."

Faris recalls being nervous during the filming of the original Scary Movie.

"There was so much raunchy stuff that I had to do and I kept wondering what my parents would think. It was probably the best way to break them it. There's not much now I could do or say in a movie that would shock them."

During her initiation to gross-out comedy, Wayans taught Faris a valuable lesson about comedy.

"One day on Scary Movie, Keenen caught me looking over at Shannon Elizabeth. She looked so gorgeous sitting there waiting for her take. I felt so dowdy by comparison and he could tell.

"Keenen told me you can't be vain and funny at the same time. He said being funny would make me a better actress."

When she was preparing for the first three Scary Movies, Faris studied the films that were being spoofed. Not this time around.

"I feel very confident about who Cindy is now. She's come into her own. She shouldn't have to imitate other people."

She acknowledges "Cindy is not the most complicated or interesting character to play, but she has been good to me."

Faris and her husband, actor Ben Indra, bought their first house after Scary Movie 3.

"We just sold our Scary Movie 3 house and bought a Scary Movie 4 one."

Faris, 29, starred as the ditzy wife in Brokeback Mountain. "I just had two days on Brokeback Mountain and I was convinced Ang Lee was going to cut my part out. He made me do my scene 15 times.

"I thought I was wrecking his movie."

Hall and Faris have vowed to do a film together that is not a Scary Movie.

"We want it to be a comedy because our on screen chemistry is as easy and organic as the friendship we've developed. Anna and I have tossed around some ideas for a buddy movie but nothing specific yet," says Hall.

She says there is already talk at Dimension Films about a fifth Scary Movie. "That's studio people talking but ultimately audiences will dictate if there will be another one."