There are bound to be interesting group dynamics when you get a bunch of Hollywood stars in the same room.

This was evident when the cast of Suicide Squad descended on Las Vegas earlier this year to promote their new film, which opens in Singapore tomorrow.

Will Smith, Jared Leto, Margot Robbie, Joel Kinnaman, Cara Delevingne, Jai Courtney, Jay Hernandez, Adam Beach, Adewale Akinnuoye-Agbaje and Karen Fukuhara spoke to The Straits Times and a handful of other press about the movie, which centres on a gang of incarcerated super-villains recruited for a covert government operation against a bigger threat.

The publicity tour for the ensemble adventure - DC Comics' answer to the success of Marvel's Avengers franchise - has stayed large on message, with an endless supply of stories about how the actors became thick as thieves on set.

But as the 10 stars huddle around a coffee table months after filming, there are glimpses of more interesting relationships on display.

Smith, the 47-year-old star of the Men In Black movies (1997 to 2012), has top billing as the marksman Deadshot and also seems to be the de facto leader of the group, even shushing his rowdy co-stars so the reporters can get a word in.

He admits that on set, "everything was a competition" - the competitors being him and male co-stars such as Kinnaman, the 36-year-old RoboCop (2014) actor, here playing a soldier put in charge of the squad, and Courtney, the 30-year-old Terminator Genisys (2015) star, cast as a boomerang- wielding assassin.

Yet the younger performers clearly look up to the rapper- turned-actor, who is arguably the biggest name on the marquee.

"If Will does anything, you think it's cool," Courtney teases Kinnaman when Kinnaman brags that he and Smith had "the exact same muscle tear in our calves" from working out.

With Robbie, Smith shares a different kind of connection from the men.

The 25-year-old, who plays the unhinged former psychiatrist Harley Quinn, was his love interest in the 2015 con-man caper Focus and the two have chemistry to spare off screen as well - Smith often pauses to tease Robbie, who frequently finishes his sentences.

But as the actors laugh and trade anecdotes, one person nobody is talking to is Leto, the 44-year-old Oscar-winning star of Dallas Buyers Club (2013), who spends most of the interview sitting quietly and staring at his lap.

Leto stayed in character as the Joker

No one seems to want to sit next to him either, so while there is a big empty space next to him, Robbie, Delevingne and Kinnaman have, almost comically, squeezed themselves onto the opposite sofa.

Smith eventually positions himself on the same couch as Leto - right at the other end - and is the first to volunteer an explanation for this awkwardness.

It began when Leto decided to stay in character as the psychopathic Joker and communicated with the rest only by sending them gifts such as a live rat and a briefcase full of bullets.

"Actually, two days ago was the first time I ever actually met Jared," Smith says. "We had never said hello and had a conversation where he wasn't the Joker."

But Leto's calculated weirdness actually helped the actors "disappear into this really strange world for six months", Smith continues. "And it was beautiful - it was one of my best film experiences."

Meanwhile, the rest were busy whipping themselves in shape for the demanding action sequences.

Says Akinnuoye-Agbaje, who appeared on the television series Lost from 2005 to 2006: "I don't think anybody would say it was enjoyable.

"But it was bonding," adds the 48-year-old, who plays Killer Croc, a cannibal with reptilian features.

"Director David Ayer has a very unique way of prepping for films. One of them was pushing us off for this very intense physical bootcamp. The great thing about that is we all went through it together - sweating and crying and moaning and fighting one another. And so you became a real unit when we came to shoot."

When the cameras were not rolling, there was barely any contact with Leto, who did not turn up for rehearsals either.

At first, his co-stars thought he was just being aloof.

"We were pissed off that he wasn't there," says 43-year-old Beach, who plays the rope expert Slipknot. "We were like, 'Who the f*** is this guy? What the hell is wrong with him - he can't even show up?' And then he showed up in a particular way…"

"Yeah, he 'showed up'. He sent a live rat wrapped up in a box," says Smith.

The group laughs at this while sneaking semi-nervous glances at Leto, who smiles, but continues to say nothing until a question is put directly to him.

Asked how he found his character, he says: "I don't really know. But the journey was really interesting. I got a sense early on that everybody had this excitement around the opportunity that was there.

"I don't know about you guys, but I always liked the bad guys - maybe because I'm a sick and broken man," he quips.

"I always related to the bad guys and this film was a fascinating experiment."

Of course, Hollywood has been more willing to cast bad guys as protagonists in recent years.

Delevingne, 23, thinks it is because audiences today "want heroes that are relatable".

"And I think that to say someone is a perfect hero is ridiculous," says the Paper Towns (2015) actress and model, who plays a sorceress called Enchantress.

In playing up those imperfections, Suicide Squad instantly differentiates itself from other superhero stories on screen.

Says Hernandez, whose character is the flame-throwing El Diablo: "People get bored of the same thing, right? I mean, sushi is delicious - but you don't want it every day."

Kinnaman agrees and believes the same thing may be happening in politics with the unexpected rise of figures such as Donald Trump, the Republican nominee for the American presidency.

"Whether it is people relating to politicians who seem like outsiders or to the do-gooder villains in this film, I think what people today really crave is authenticity.

"And I think people relate to the bad guys in that way because they just are who they are and they don't care what people think. That's the thing that draws people to them."

•Suicide Squad opens in Singapore tomorrow.