Just when Marvel's 'Avengers: Age of Ultron' gears up to hit theaters worldwide, film's director Joss Whedon can't help but be anxious about it thinking that he "can't try to replicate the success" of the first film garnering a total of $1.5 Billion from the second one.

Well, there is no number yet but reports claim that Whedon has nothing to worry about as the sequel is doing good already despite his previous worries. "The competition that I'm in is with myself. Can I make a better film? That is enormously cumbersome. I do not sleep at night. I can't try to replicate the success," he told E! News in an interview last summer during one of their filming days.

"I can try to remember what worked and do it again so that people do come in getting an Avengers movie. I don't want to trick them. I don't want to do a bait and switch, but at the same time, all I want to do is get more out of this than I got out of the first one," he added.

As the fans anticipate the coming of the film which premieres on May 1, Whedon also gave some pretty big revelations about how they chose the many new characters for the sequel. "We've increased the number of characters," Whedon said, "not because we want to throw more stuff against the wall, but because we want to be able to look tour characters in a different light and sort of increase or palate and do different things in different places and get more perspectives."

Not only will the sequel take in the original star studded cast in Avengers like Robert Downey Jr. as Iron Man, Chris Evans as Captain America, Chris Hemsworth as Thor, Samuel L. Jackson as Nick Fury, Scarlett Johansson as Black Widow, Jeremy Renner as Hawkeye, Mark Ruffalo as The Hulk and Cobie Smulders as agent Maria Hill, the film will add more star studded cast.

The new members of the film includes Hayley Atwell (Peggy Carter),Don Cheadle (James "Rhodey" Rhodes/War Machine), Idris Elba (Heimdall),Anthony Mackie (Sam Wilson/Falcon) and Stellan Skarsgård (Erik Selvig). The famous Ultron is reportedly played by James Spader who Whedon really wanted to have and apparently didn't have any trouble getting him.

Apparently, once Whedon brought the suggestion to the management, they all agreed in an instant saying "Spader, they're like, 'Oh, yeah! We love him! Great!" he said, "Like, 'Aren't we going to fight? You're a studio! Don't we fight?'" he added.