Originally Laurence Fishburne was keen to provide the voice for Galactus. He happily switched to the role of the Silver Surfer when it became clear that Galactus was not going to be represented in "human" form.
For Michael Chiklis's performance as the Thing, a new set of prosthetics were developed. These prosthetics were easier for Chiklis to wear, as they provided better ventilation and could be easily removed, in comparison to the previous film's prosthetics which required six hours to apply, were uncomfortable and could not be easily removed.
Supporting character "Captain Frankie Raye" shares her name with comic-book super-hero Nova's alter ego. In the comic-books Frankie Raye was a love interest of Johnny Storm and, as Nova, succeeded the Silver Surfer as herald of Galactus.
For this outing, some slight revisions were made to the make-up of The Thing, giving him a larger brow and broader shoulders. This brought the design more in line with the current comic book incarnation.
In the original script, it was Reed's idea to have Johnny assume all the team's powers to fight Dr. Doom; and Johnny had to be talked into it. Tim Story later made it Johnny's idea, to make the scene Johnny's big moment and give Chris Evans a chance to really shine.
Jessica Alba, reacting to criticism about her performance in this film, said that the director, Tim Story, told her "It looks too real. It looks too painful. Can you be prettier when you cry? Cry pretty, Jessica ... Don't do that thing with your face. Just make it flat. We can CGI the tears in".
Tim Story wanted the Four's iconic laying-on of hands to serve a practical purpose in the film, not to be just a go-team gesture. Hence its use in the scene where Johnny assumes all of the team's powers in order to fight Dr. Doom and the Surfer's board.
Jessica Alba stated in an interview, that she didn't want to do another "Fantastic Four" film. A 3rd installment was abandoned and instead, the franchise was reboot in 2015 and Kate Mara took over the role of Susan Storm.
as a guest who is refused entry to the Fantastic wedding. This is in keeping with the 1960s "Fantastic Four" comic, where at Reed Richards and Susan Storm's wedding, two characters, obviously representing writer Lee and artist/plotter Jack Kirby, are also not allowed to attend the wedding.
The trivia items below may give away important plot points.
Although the film uses the premise that the Silver Surfer gets his powers from his board, this is clearly not the case in the comics. In the comics, the Surfer is able to fly on his own and use his full gamut of powers without the aid of his surfboard. He uses it, however, as it significantly decreases the energy required for flight.
According to Don Payne, the film was influenced by the Fantastic Four comic "The Galactus Trilogy" (Galactus and the Surfer approach Earth), "Fantastic 4" issues #57-60" (Dr Doom steals the Surfer's powers), and the "Ultimate Marvel" comic "Ultimate Extinction" (the name of Gah Lak Tus is used).
Tim Story once said that he would never have giant robots in any of his movies. In this film, Galactus, normally portrayed in the comics as something resembling a giant robot, is shown as a giant cloud. However, two hints to his physical appearance in the comic book are included in the film. Both the shadow on Saturn as he passes by it and the fiery mass within the cloud, resemble his signature helmet.