Writer-director Todd Phillips began his film career making documentaries (“Hated,” “Frat House,” “Bittersweet Motel”), but in 2000 he segued into comedy with the surprise hit “Road Trip,” which he followed up in 2003 with the smash “Old School.” His next picture, the comic updating of “Starsky and Hutch,” came in 2004. Now he’s back with a loose remake of the 1960 English comedy “School for Scoundrels,” transposed to New York and starring Jon Heder (“Napoleon Dynamite”) as a sad-sack fellow who enrolls in a class in self-assertion taught by an abrasive (and, as it turns out, unscrupulous) instructor (Billy Bob Thornton). Unfortunately, the two men become rivals fighting over a girl, and try to outwit one another to win her, using any means necessary.

“I had seen the original…and thought it was a solid film,” Phillips said during a recent Dallas interview. “I love those movies, but a lot of those Ealing comedies feel a little bit restrained, in a way. I thought it was a solid premise with some funny stuff, but…I always felt it was holding back. But I really thought it was a good concept, and what I took from it was the idea, because story-wise, ours goes in a different direction: what if there was a teacher who gave hope to the hopeless? We [Phillips and collaborator Scot Armstrong] kind of went off on that premise.”

“We wrote the script with Billy Bob in mind,” Phillips continued. “Not that we wrote it in his voice, or wrote it for him. But we definitely were thinking, ‘Boy, it would be cool to get Billy Bob for this!’ He does mean really well, but people still love him. Billy gets away with murder, both in real life and in the movie.” When the script was finished, it was sent to Thornton, who accepted the part.

The next step was to find the right actor to play against Thornton. “Once Billy said yes, it was about finding someone who was his direct opposite,” Phillips explained. “This is not a buddy comedy, so it’s not about chemistry, it’s about tension. It’s sort of anti-chemistry, in a way. And you couldn’t find someone more different from Billy Bob Thornton than Jon Heder. If Billy Bob is the Antichrist, then Jon is a glass of milk. From the first frame people are on his side. Audiences just root for him.”

But Thornton and Heder aren’t the whole movie; they’re surrounded by the likes of Michael Clarke Duncan and Ben Stiller, as well as a whole classroom of stand-up stars. “Probably the seven biggest improv guys in New York are in that class,” Phillips said. “For me it was just about having a lot of funny people on the set. I always try to cram as many funny people into a comedy [as I can], just to keep it alive on the set–the feeling that anything can happen.” He added, “Casting is 70% of the battle. It’s never difficult once you’ve got the ensemble rolling. I like to keep [the shoot] pretty loose, because it’s important to keep the energy up in a comedy. It’s really more an energy thing when you’re directing than it is about the lines.”

But, Phillips emphasized, there was another important element. “The one thing we try for,” he said, “is that there’s an emotional through-line that the audience buys into, so when we put the characters through things, it’s funnier because you care about them. That’s what the job of the director is–balancing that tone and keeping that emotional story alive while still being funny.”