The plan Wednesday night for Jon Heder was to attend the Los Angeles premiere of his new movie with Will Ferrell, Blades of Glory – but the any-moment-now-father-to-be also had another duty: being on maternity call.

"I have my phone on me, it could be any second," Heder, patting his jacket pocket, told PEOPLE before the screening at Grauman's Chinese Theater in Hollywood.

Heder's pregnant wife, Kirsten, also attended the premiere, but the couple were prepared to call the doctor at a moment's notice.

Asked if he might even bolt from the theater during the middle of his movie, Heder looked down the red-carpet line of reporters still hoping to talk to him and said, "Just as long as I get some of these interviews done. You could be the last."

Heder, 29, and his wife – who met when they were both students at Brigham Young University in Provo, Utah – are expecting their first child. The actor, who is from Salem, Ore., burst upon the scene playing the memorable goofball Napoleon Dynamite in the 2004 film of the same name.

As for how costar Ferrell thinks Heder will do in the daddy department, the star, 39, tells PEOPLE: "I think Jon will make a great father. He's a good listener, and he likes children, that's important. You should like children to be a father."

Ferrell is speaking from experience. "I mean, I found that out the hard way, 'cause I hate children, and now I've got two," he says. "But I love them, 'cause they're my children, but...."