Jeff Nathanson met with Spielberg and Lucas in August 2004, and turned in the next drafts in October and November 2005, titled "The Atomic Ants". David Koepp continued on from there, giving his script the subtitle "Destroyer of Worlds", based on the Robert Oppenheimer quote. It was changed to "Kingdom of the Crystal Skull", as Spielberg found this a more inviting title which actually named the plot device. Koepp wanted to depict the character of Mutt as a nerd, but Lucas refused, explaining he had to resemble Marlon Brando in "The Wild One"; "he needs to be what Indiana Jones' father thought of  – the curse returns in the form of his own son – he's everything a father can't stand". Koepp collaborated with Lawrence Kasdan on the film's "love dialogue".