If you directed a movie that was the third highest-grossing film of all time and left fans wanting more, it would seem a no-brainer to make a sequel.
Yet film-maker Joss Whedon admits he did not really know what he was getting into when he agreed to do a follow-up to The Avengers.
In 2012, his story about a group of superheroes who save the world earned more than US$1.5 billion, a haul surpassed only by Avatar (2009) and Titanic (1997).
The film also broke new ground by combining characters from four distinct comic-book franchises - Iron Man, Thor, Captain America and the Hulk - who team up to stop Thor's evil brother, Loki.
But the sequel, Avengers: Age Of Ultron, would be an even bigger undertaking, expanding the already crowded cast to include additional heroes and villains from the Marvel universe.
Life! and other media get a taste of this superhero-saturated world at a chaotic press conference in Los Angeles, where Whedon gathers 10 members of his ensemble, including Robert Downey Jr (Iron Man), Chris Hemsworth (Thor), Scarlett Johansson (Black Widow), Chris Evans (Captain America), Mark Ruffalo (the Hulk), Jeremy Renner (Hawkeye), Aaron Taylor-Johnson (Quicksilver), Elizabeth Olsen (Scarlet Witch), James Spader (Ultron) and Paul Bettany (Jarvis).
Once the eyes in the room adjust to the glare of all that star power, it becomes apparent that getting this bunch to sit still and answer questions will be like herding cats, the actors more intent on goofing around, teasing and occasionally ganging up on one another than promoting their blockbuster film, which is already predicted to set new box-office records.
So one can only imagine what it was like for Whedon to oversee a US$250 million (S$336.6 million) movie with this bunch and dozens of other performers.
Indeed, the 50-year-old has the look of a man who has only just escaped it all with his sanity intact - but he plays this for laughs when asked about the hurdles he encountered in making the film, which opens in Singapore on Thursday and took him two years to write and direct.
"Um, there's like 47 of these people - I really didn't think that through," says Whedon, who also wrote and directed the first movie. "And I regret very much doing this at all."
The main challenge was ensuring the story did justice to the characters, each of whom has a rich mythology and fan following from the comic books and other films adapted from them, such as the hit Iron Man, Thor and Captain America franchises starring Downey, Hemsworth and Evans.
As Whedon has conceded in other interviews, having 11 main characters in a movie was "frankly too much". "It's just making sure that everybody's got his moment, everybody's got his through-line and that it's connected to the movie," he says of the sequel, which sees the gang confronted with a new threat as Ultron, a peacekeeping robot created by Iron Man, runs amok and tries to destroy the planet.
Looking down the table at the long line of actors, Whedon adds: "I have all these people - I love all these people, they're extraordinary - but making sure they're all within the same narrative structure, that it's all connected to the main theme… at some point in the editing process, I could not have told you who they were, who I was, what movie I was making. I got so lost in it.
"But I think it all came together. It's just about making these guys look good, which takes a long time."
It probably takes a lot of patience too, if the dynamics among the cast on display are any indication.
As Whedon speaks, Evans, 33, Hemsworth, 31, and Renner, 44, are like restless schoolboys sitting at the back of the class, whispering in-jokes and pulling faces at one another throughout the question-and- answer session.
Evans and Hemsworth, who share top billing with Downey, 50, bat aside any attempt to get them to talk at length about their characters, apart from joking that their favourite superheroes when they were growing up were, of course, Captain America and, for the Australian Hemsworth, "Captain Australia".
Downey clowns around too, responding to a question about his role as the billionaire inventor- turned-superhero Tony "Iron Man" Stark by feigning a diva-like tantrum.
"The next time I'm not asked the first question…" he says threateningly, the expletives that follow drowned out by his castmates' laughter.
But he also stops to praise the director and, in doing so, inadvertently reveals that a big part of Whedon's job may have been to wrangle and appease some supersized Hollywood egos.
"I read Joss' script and I said, 'I think this is great'," says Downey, whom Forbes magazine last year named the highest-paid actor in Hollywood, thanks to his Avengers and Iron Man pay cheques.
He adds: "I thought it was a Swiss watch to begin with and Joss really created some great new situations for Tony to be in. So rather than digging in my heels and trying to rewrite every scene to make it even better if possible, I just showed up and it turned out great."