When Marvel Studios announced that Paul Rudd — best known for his comedy work in such films as “The 40-Year-Old Virgin,” “Anchorman” and “Clueless” — would star as Ant-Man in their bigscreen adaptation, Rudd understood that some fans might be skeptical about him playing the beloved comic book superhero, who shrinks to insect size to battle crime.

“When people heard that I was cast in this movie, I think most people’s reactions were ‘Huh? Paul Rudd as a superhero? Really?'” Rudd told Variety Monday night at the film’s Cinema Society screening in New York at the School of Visual Arts Theater.

“The majority of my career has been doing comedies and I was always that guy, so I completely understand. Playing a comic book character is different from anything I have ever done before and that was a huge appeal to me. I wanted to do something unexpected. I’m grateful that Marvel took a chance with me. It’s been really gratifying.”

In “Ant-Man,” Rudd not only made his leading man debut in a Hollywood tentpole, but also co-wrote the screenplay, which centers on a father-daughter relationship.

“It’s an emotional story that people can get invested in,” he said. “We wanted to make sure the movie had heart and be funny with all the action.”

Michael Peña, who plays a crook and Rudd’s friend, nearly steals every scene he’s in with his dim-witted jokes. The “Crash” actor says he did some improvising to get the big laughs in the film.

“My performance was probably 50 percent improv,” Peña said. “When I study a script, I want to do different takes and try to change it up. I like to rehearse a lot, so all of these ideas came up when Paul and I were rehearsing. Thank God Marvel was like, ‘If you want to try it, do it.’ Paul was really instrumental with the jokes. We’d come in in the morning and we’d re-write some stuff and he was really good with that. It allowed me to open up. Paul is the best at improv. He can do it for days.”

Costar Michael Douglas admits he did not read comic books growing up, but jumped at the chance to star in “Ant-Man” — his first superhero movie and first family-friendly film.

“Most of my career has been R-rated,” Douglas told Variety. “My children haven’t seen most of my pictures. But when I told my son about ‘Ant-Man,’ he said, ‘Dad, you have to do this.’ He was like my agent. I’m glad I took his advice. It turned out really well.”

To portray a superhero, Rudd listened to Chris Pratt, his “Parks and Recreation” costar, on how to bulk up and look like a fighter.

“I basically didn’t eat anything for about a year,” said Rudd, who shows off his washboard abs onscreen. “I took the Chris Pratt approach to training for an action movie. Eliminate anything fun for a year and then you can play a hero.”

As for donning the Ant-Man suit, “It was just cool all the way around,” Rudd said with a big smile. “I felt like the part in that thing. It was a lot of fun. It got a little toasty, but it was never debilitating.” Asked if there any problems going to the bathroom in the suit, Rudd quipped, “No. I’m thankful they planned ahead!”

Following the screening, Rudd, Douglas and Peña joined costars Corey Stoll (“House of Cards”) and Bobby Cannavale at the rooftop of the Knickerbocker Hotel located in Times Square for the after party. Other notable guests included “Girls” actor Andrew Rannells and actress Malin Akerman.