Barbra Streisand, Seth Rogen on their 'Guilt Trip' comedy travels For the first time during a boisterous joint interview with Barbra Streisand, who plays his mother in the new comedy "The Guilt Trip," Seth Rogen seemed at a loss for words. The question posed was straightforward: Did he grow as an actor working with veteran Streisand ("Funny Girl," "The Way We Were," "Yentl," "A Star Is Born") in the buddy comedy opening Wednesday? But Rogen hesitated. "I don't know," said Rogen, 30. He looked over at Streisand, one of a relative handful of entertainers who have won an Emmy, Grammy, Oscar and Tony, sitting next to him on a sofa at a Beverly Hills hotel room. "What are you going to say?" he asked her. Streisand, a vibrant 70, smiled sweetly at her reel-life son and began to talk about the scene in which warmhearted widow Joyce Brewster and her inventor son Andy stop to visit his ex-girlfriend during their cross-country road trip. Joyce thought that the girl had broken up with her son in high school, but during the visit she learns that it was her son who ended the relationship. "He was really fabulous in the scene," she said, glancing over at Rogen. It's very quiet. it's very internal and yet you can feel his pain. He didn't take the funny road, the easy road. I was very impressed. "It's way easier for me not to be funny," Rogen admitted to Streisand. It is like an effort to think of jokes tonally that work in the movie and work with the characters. I have done some movies recently that have tricky tones. They deal with serious stuff. Like if '50/50' wasn't a comedy, it would have been easier to make. Just a few hours before the Los Angeles premiere of the "The Guilt Trip," Streisand and Rogen were holding court, sharing an easy rapport despite their four-decade age difference. Streisand was the picture of low-key elegance, wearing a flowing black top adorned with several long chains. Rogen had upgraded his usual street look with a black cardigan, white T-shirt and dark jeans. Rogen was still finding out things about his iconic screen mom. He broke into a hearty gale of laughter when he learned that she played a hooker in the 1970 comedy "The Owl and the Pussycat." "You'd like the movie," she told Rogen, smiling. It's Buck Henry. "I love Buck Henry," said Rogen. "He wrote it," she said, adding that Marilyn Chambers of the X-rated classic "Behind the Green Door" is in the movie. "Marilyn Chambers played Robert Klein's girlfriend," quipped Streisand, nudging Rogen on the arm. At first glance, the pairing of actress-singer-director-producer Streisand and Rogen, the affable yet edgy star of such raucous R-rated comedy hits as Judd Apatow's "Knocked Up," seems a mismatch of acting styles and comic sensibilities. There's also a generation of audiences that knows Streisand primarily for her supporting roles as Ben Stiller's free-spirited mother in 2004's "Meet the Fockers" and 2010's "Little Fockers." In fact, "The Guilt Trip" features Streisand's first starring role since 1996's "The Mirror Has Two Faces," which she also directed and produced. But director Anne Fletcher ("The Proposal") had a gut instinct they would work beautifully together. "Barbra has seen and done everything under the sun and brilliantly, and Seth is an amazingly accomplished young person in the industry, but at the end of the day they are actors," said Fletcher. The thing I get giddy about is that you can have the biggest star in the world on the set with her notes and suggestions and hair and makeup and she's ready to be Joyce Brewster. "The Guilt Trip" is about a lot more than a Jewish mother haranguing her adult son during an eight-day road trip. It's a journey of discovery as they break down the misconceptions of each other as they travel from New Jersey to San Francisco. Along the way, Streisand's Joyce gets drunk, enters into an eating challenge at a steak restaurant, attracts the attention of a handsome cowboy and even gets her ears pierced. And Joyce learns that Andy is far from the success she thought he was and that there is a lot of pain under his bravado. "That's why I liked the story," said Streisand. It's about transformation. It's about growing up. You start one way and you end up another way. It's more than a guilt trip; it's an education trip.