New releases? No threat to "Tropic Thunder"! Well, not a big one anyway.

That action-comedy defended its turf to stay perched at the top of the box office for a second straight weekend, taking in $16.1 million, according to studio estimates released Sunday.

But hot on the tail of Ben Stiller, Robert Downey Jr. and company was "The House Bunny," which earned $15.1 million in its debut weekend. "Death Race," an update of 1975's "Death Race 2000," opened at No. 3 with $12.3 million. Rounding out the top five were "The Dark Knight," which pulled down $10.3 million more, and "Star Wars: The Clone Wars," which made $5.7 million.