Beware when entering the office of Johnny Knoxville.

He’s known for greeting guests with a blow-dart gun, hitting one recent visitor in the thigh and buttocks. Letting one’s guard down around the star of the “Jackass” film franchise is never a good idea.

After the giggling stops and the blow-dart gun is put away, Knoxville, a 41-year-old father of three, gets serious about working with Arnold Schwarzenegger on the film “The Last Stand,” in theaters Friday.

“He’s really gregarious,” Knoxville says of Schwarzenegger, who returns to acting after serving as governor of California.

Knoxville’s co-star is not the type of person on whom you’d use a blow-dart gun, but “he seemed pretty happy to be acting again. His enthusiasm spread around the set. He was so down-to-earth that it helped take away (the surrealism) of acting beside him.”

Knoxville plays Lewis Dinkum, who owns an artillery museum and has always looked up to Schwarzenegger’s character, Sheriff Ray Owens.

Lewis has dreams of being a deputy, but he’s “a little too spacey” for the job, Knoxville says.

When members of a drug cartel hit town, it’s up to the sheriff and Lewis to battle them before the bad guys can reach the Mexican border and hide from U.S. officials.

“I actually have scenes where I shoot out the bad guys with Schwarzenegger. How cool is that?” Knoxville says. “I don’t remember being nervous. I just remember it being fun, putting all my energies into making this fun and not messing up.”

The day when he was shooting a scene in a bus, with Schwarzenegger, jolted Knoxville (nee Philip John Clapp) as being dreamlike.

“I thought, ‘Here I am, about to shoot it out with Schwarzenegger.’ It was unreal,” he says.

“I mean, ... I remember going to the movies back in Knoxville (in Tennessee) as a kid and seeing his early work, and now I am working with him. Wow.”

Though his cinematic history is checkered with more flops than hits, Knoxville doesn’t mind. He says he picks projects based on who’s directing, who’s writing or with whom he will get to work.

The “Jackass” films are lucrative. His other movie projects have been more about learning from the industry.

From “Stand,” Knoxville has realized he wants to do more action movies. Up until now, he’s either done numbskull flicks such as “Jackass” (all three in the franchise have debuted at No. 1 at the North American box office) or broad comedies.

“Daltry Calhoun,” which came out in 2005, featured Knoxville in a dramatic role, playing a reluctant small-town father.

“I’m looking now for action-movie roles,” he says. “I’m looking at some in development. So that’s the goal. I think I would be credible in (action-movie) parts.”

Despite the fact that he subjects his body to pain in his “Jackass” movies, he was not allowed to do his own stunts in “Stand.”

“In (non-‘Jackass’) films? I rarely get to do my own stunts” because of insurance reasons, Knoxville says.

Next up for Knoxville is a role in the comedy “Movie 43,” which opened Friday. It is an outlandish collection of short films featuring an A-list cast, including Hugh Jackman, Naomi Watts, Kate Winslet, Emma Stone, Terence Howard, Halle Berry, Gerard Butler, Anna Faris, Chris Pratt, Richard Gere and Elizabeth Banks.