Stiller Joines the R-Rated Bomb Club

Summer hasn't been kind to two of Hollywood's biggest comedy stars.

Ben Stiller's The Watch, co-starring Vince Vaughn, Jonah Hill and Richard Ayoade, opened to a feeble $12.8 million, even lower than the $13.5 million June debut of Adam Sandler's That's My Boy. What happened? Some blame the R ratings assigned to both films. Like Sandler, Stiller, 46, has broad appeal in all-ages pics (Night at the Museum, Meet the Parents), but insiders say Stiller signed on to Watch only after the Fox studio agreed to amp up the raunch factor. He's had success with R-rated films before -- 1998's There's Something About Mary ($370 million worldwide), 2008's Tropic Thunder ($188 million) -- but moviegoers are tougher to hook in today's times, so the more that are allowed in the better. Next up for Stiller: a PG-13 remake of The Secret Life of Walter Mitty that opens Dec. 25, 2013.