You might think anything goes with Jackass, but there’s actually a complex system in place to ensure the most awesome Jackassery happens safely. Number one rule: You must be sober to dive into poo.

“It’s been a rule forever,” director Jeff Tremaine said. “You don’t do stunts if you’ve been partying that day. But right after... You can do in hung over but if I know someone’s been drinking or doing something else, then they don’t shoot that day. I might find out later that Preston did some Xanax the day he did the King Kong bit. He was terrified of heights one day and the next day, ‘Oh, no problem. I’ll climb up there.’ I should’ve known something’s up. Even Steve-O at his worst, I don't think you were ever wasted during a stunt. The guys are never wasted during the stunt. You might get wasted right after. The guys watching it might get wasted but even buzzed.”

More insider info after the jump...

Steve-O is two years sober now. That actually means he’s more available for crazy Jackass bits in Jackass 3D. “There were some times when I wasn’t allowed to shoot,” Steve-O said. “Like the branding thing [in Jackass: The Movie], there were times where I was up for something but I was intoxicated so I wasn’t allowed. Nobody wants to see us really wasted I don't think.”

There are also limits to how much a single performer is allowed to film. “To stop shooting, they lured me to the office for one reason,” Johnny Knoxville said. “Then they all got me into a big room, like ‘We’re out of time. The editors are bottlenecked with footage. You have to stop.’ It’s just fun, man, and I do get obsessed with constantly all day long thinking of ideas, but that’s just how it is.”

The rules get complicated when pranks are involved. Bam Margera or Danger Ehren might be working on a stunt, but Johnny Knoxville or Wee Man could be planning a prank on them. “It’s tense on the set because you can expect something horrible is going to happen to you,” Steve-O said. “After it does, you’re generally pretty happy that it did but you’re looking over your shoulder the whole time. I remember the tensity [sic] on the set just reached a fever pitch on the day that I got my nose broken.”

Some of the guys have learned how to make themselves prank proof. Chris Pontius doesn’t get messed with that much. “That was too tense where it was hard to actually do the work that we needed to do,” Pontius said. “Usually if you’re going to be someone that gets involved in these side pranks, if you don’t get involved in it it’s not going to really happen to you that much really. It will a little bit. A friend told me like the Hell’s Angels when they move into some neighborhood and set up a clubhouse, I asked, ‘Do they ever have to deal with any trouble?’ He’s like, ‘No, they set examples years ago.’ So whenever anyone ever did anything unnecessary back to me, like Mike Ellis did something very unsportsman-like to me, I do something 10 times worse in front of everyone. It makes you not have to worry about it as much because they know.”

When it comes to writing a bit, individuals contribute ideas but also take hints from the crew, camera, etc.  Once everything is filmed though, it’s up to the whole gang. Wee Man explained it takes a unanimous decision to choose the final array of stunts for the film.

“We all kind of decide once something gets filmed,” Wee Man said. “Even if we go and spend a little money to make something big and awesome, we could film something on the side of it just pranking each other that turns out way better. Then in the long run it depends on once we’re putting the movie together, what makes all of us laugh and we think is super awesome. So it’s not just one person going oh, cut that, put that, cut. It’s everybody’s input on it.”

The criteria is simple, said Preston Lacy. “The laugh meter is really what does it,” Lacy said. “If everybody’s laughing, it’s gonna make it.”

It does seem like when things get really dangerous, if someone says “Stop,” the rest of the crew respects that. At least on camera, we see the crew pause to let the performer back off. Maybe it’s tricky editing, because the gang says they don’t even trust the group safe word.

“[Say] ‘Oklahoma’ and that’ll buy you about 30 seconds,” Lacy said. “’Oklahoma,’ Trip Taylor will back them off of you for maybe a minute, but then it’s back on.”

Even if he goes to the hospital, Ryan Dunn is suspicious of anyone who examines him. They might be a ringer for another prank. “It usually doesn’t end there either,” Dunn said. “I don’t trust a doctor, I don’t trust anybody. Once those wheels start turning it’s tough to stop that train.”

Jackass 3D opens Friday.