LOS ANGELES (AP) – Movie-goers were easy prey for a double dose of space invaders.

The sci-fi smackdown “Alien vs. Predator,” featuring the creatures of the “Alien” and “Predator” franchises, debuted as the No. 1 weekend movie with $38.25 million, studio estimates showed Sunday.

“Princess Diaries 2: Royal Engagement,” with Anne Hathaway and Julie Andrews reprising their royal roles, opened in second place with a three-day gross of $23 million, pushing its total since premiering Wednesday to $37.2 million.

That was about on par with the $37.9 million “The Princess Diaries” took in over its entire first week in August 2001.

The new movies bumped the previous weekend’s top film, Tom Cruise’s “Collateral,” to third place with $16 million.

“Alien vs. Predator,” featuring Sanaa Lathan and “Aliens” and “Alien 3” co-star Lance Henriksen, centers on a human expedition that stumbles on a space-monster blood feud in an ancient pyramid buried below Antarctica.

The movie debuted slightly ahead of the $36.4 million debut of last summer’s horror hybrid “Freddy vs. Jason,” which paired the slashers of the “Friday the 13th” and “A Nightmare on Elm Street” franchises.

“This continues the trend of combining franchises to very strong box-office results,” said Paul Dergarabedian, president of box-office tracker Exhibitor Relations. “If you’re a fan of the ‘Alien’ movies, you want to see this movie. If you’re a fan of ‘Predator,” you want to see this movie.”

Audiences shelled out $16.8 million to see “Alien vs. Predator” on Friday, but the movie’s gross fell to $12.5 million Saturday, a steep 26 percent decline. Most new movies do better business on Saturday than Friday.

That’s a sign that “Alien vs. Predator” could follow the pattern of “Freddy vs. Jason” and other horror tales, which tend to open well then plunge in subsequent weekends.

Still, “Freddy vs. Jason” topped out at a healthy $82.2 million domestically. Budgeted at $60 million, “Alien vs. Predator” would turn a solid profit for 20th Century Fox if it matches the gross of “Freddy vs. Jason.”

Preceded by “Alien vs. Predator” video games, the movie drew a largely male audience, most younger than 25. To broaden its appeal, 20th Century Fox brought the movie in at a PG-13 rating, though the previous four “Alien” films and two “Predator” flicks had hard R ratings for violence.

“I don’t think it’s a cop-out at all,” said Bruce Snyder, the studio’s head of distribution. “This is based on a video game that did have a bit of a younger audience. There’s a lot of action and violence, but most of it is creature to creature rather than creature to people.”

In limited release, the domestic drama “We Don’t Live Here Anymore,” starring Laura Dern, Naomi Watts, Mark Ruffalo and Peter Krause, opened strongly with $106,000 in just seven theaters. The film expands to more theaters this Friday.

Estimated ticket sales for Friday through Sunday at North American theaters, according to Exhibitor Relations Co. Inc. Final figures will be released Monday.

1. “Alien vs. Predator,” $38.25 million.

2. “Princess Diaries 2: Royal Engagement,” $23 million.

3. “Collateral,” $16 million.

4. “Yu-Gi-Oh! The Movie,” $9.4 million.

5. “The Bourne Supremacy,” $8.3 million.

6. “The Village,” $7 million.

7. “The Manchurian Candidate,” $6 million.

8. “Little Black Book,” $3.7 million.

9. “I, Robot,” $3.6 million.

10. “Spider-Man 2,” $3.4 million.

AP-ES-08-15-04 1352EDT