Santa needs spanked. But in the new movie, “Bad Santa,” he might not consider it a punishment.

“Bad Santa,” starring Billy Bob Thornton opens today, and though it does not have the wholesome holiday goodness of “It’s a Wonderful Life,” or “How the Grinch Stole Christmas,” it uses the vulgarity style of “South Park” to elicit Christmas spirit.

“I love the formula for Christmas movies. They are about someone who gets lost and finds themselves along the way,” said Billy Bob Thornton, who plays Willy, the film’s title character.

And this is what happens in “Bad Santa,” but not without a lot of cursing, sex, booze and cigarettes. This vulgarity does not disappear by the end, setting it further apart from other Christmas movies.

“If the movie had become too sentimental at the end it would not have worked,” Thornton said.

And, of course, the never-ending sins in the movie add to its appeal, because it creates irony and humor in this sin-filled holiday joy.

Willie drinks himself into oblivion every year around Christmas with the help of his friend Marcus, played by dwarf Tony Cox. They find jobs together at a local mall playing Santa Claus and his little helper. On Christmas Eve the audience finds out that Willie has a talent for breaking open safes and Marcus can expertly disarm security systems, making them the perfect criminal pair as well.

Thornton said these sins provide some of the similarities between Willie and himself.

“I felt like a loser when I was growing up like Willie and he likes beer, cigarette, and women,” Thornton said.

Other characters in the movie include Sue (Lauren Graham), a young bartender who has a “thing” for Santas. Thornton said some of the most ad-libbed parts of the movie are with Graham.

Thurman Merman, also known as “the kid,” is played by newcomer Brett Kelly.

Thornton said Kelly was a smart, terrific kid who was as curious as his character in the movie.

“Bad Santa” was directed by Terry Zwigoff, best known for directing Thora Birch and Scarlett Johansson in the indie smash “Ghost World.” He also directed the highly acclaimed documentary “Crumb,” the story of underground comic book artist R. Crumb.

“Terry likes the actors to do their thing. Maybe because he is used to working with real people,” Thornton said.

Thornton said working with Zwigoff was a great bonus to a wonderful script and character. As much as he liked the character, however, he said the most challenging part of the movie was playing Willie each day.

“The biggest challenge was totally committing myself to this sad, sad character. I had to dissappear into a character I have seen before. I know guys like this,” Thornton said. “I was not actually drunk. I sure looked like it though.”

And Thorton did conquer this part of the role well, as if he were a natural. His skinny, worn-looking frame and tousled hair was the perfect look for the most drunken, pathetic looking Santa Claus most mall supervisors have ever laid eyes on. It is part of the humor of the movie that mall managers hire Willie and Marcus despite their rag tag appearance and offensive language.

The manager of the Phoenix mall where most of the movie takes place is Bob Chipeska, played by the late John Ritter in his last film role. He hysterically portrays the movie’s mall manager.

Thornton said he and Ritter were longtime friends.

“It was a joy to work with him as it always was. We were almost like brothers. It was like the old days. He cracks me up,” he said.

Bernie Mac, the successful comedian with his own self-titled show, is the mall detective who works with Ritter to put an end to the sinful Santa’s antics. Mac’s sarcastic character is the perfect match for Ritter’s bumbling, idiotic mall manager. Their scenes together add a nice sideshow to Thornton and Cox.

Despite the lack of holiday schmaltziness in “Bad Santa,” Thornton said he loves the Christmas season.

“I am very sentimental about Christmas. I have two boys – 9 and 10 years old. We have really traditional Christmases,” Thornton said.

He said he has run into a ‘bad santa’ before when he took his boys to the mall to visit Mr. Claus.

“I took my kids to the mall one time and I am pretty sure that Santa had a few cocktails,” Thornton said.

Rumors are afloat that the Walt Disney Co. – who produced the movie – have found the movie to be too controversial. These allegations are false, Thorton said. He said Disney knew full well what was involved in the film, and thought it was a good idea. If there is a problem he said he does not understand why.

“I do not understand controversy with movies. I just wish they would all just shut the f*** up,” Thornton said.

Maybe the movie is not for young children, but if it catered to everyone it would lose some of its entertaining and comedic qualities.

“I think people from 17-75 years old will be laughing their butts off,” Thornton said. “The audience will get the s*** entertained out of them.”