Emma Thompson almost made an accidental uncredited cameo in this movie, while visiting friend Liam Neeson on the set. Thompson, who'd been filming Nanny McPhee Returns (2010) in an adjacent studio, went to visit Neeson during a break, just as Neeson was about to shoot a scene with Ralph Fiennes and Danny Huston. Unable to exit the set fast enough, as the cameras began to roll, Thompson, in her clumsy Nanny McPhee costume, had to hide behind Huston's throne during the take, so she would not be picked up by the cameras.
The mechanical owl Bubo, from Clash of the Titans (1981), has a cameo as the toy Perseus picks up before he leaves on his quest. According to the filmmakers, the cameo was widely debated as to whether to keep it in the film, or not. It was eventually decided to keep it in the film, to please the fans of the original film.
Although Greek mythology contains different versions of the story of Perseus, the film deviates from all of them in some parts. Perseus supposedly flew to an island using winged sandals he borrowed from Hermes, and Medusa was only one of three Gorgons (i.e. half-woman half snake creatures with serpents for hair, the other two were called Stheno and Euryale).
The word Kraken (sea monster) is Norwegian/Swedish, not Greek. Early script drafts considered changing it to its Hebrew counterpart Leviathan (famous from the Bible hymn of Job 41). It was changed back to Kraken as a tribute to the original Clash of the Titans (1981) tagline "Release the Kraken!" Surprisingly, the creature's Greek name, Cetus, was never considered.
Concept Designer Aaron Sims considers designing Medusa his most difficult task: "Are they all the same snake in her hair? Do they look more like hair? Are they different in silhouette or in light? And how much of a human face does she have, or is it more like a snake? I worked on one design, and people said it reminded them of Lord Voldemort, because there was no nose. You have to be careful, so it still looks like it's an original idea."
This film begins with a set of constellations portraying history's events. Clash of the Titans (1981) ended with a set of constellations portraying history's events (though not the same constellations).
Sam Worthington stated in an interview, that Perseus was meant to start out the film with long hair, but would cut it short, before going off on the journey. This idea was scrapped, because they felt the scene didn't work, and Perseus was given short hair throughout the whole film.
In later interviews, Louis Leterrier would disown the film, claiming that the 2-D to 3-D conversion, was a studio decision that was forced on him, despite his attempts to point out that it wasn't working. He now says "it's not my movie", and the experience of dealing with that, made him choose not to return for the sequel.
Originally, Perseus was envisioned as being more of a young slender man. Louis Leterrier had watched Sam Worthington in the film Somersault (2004), and thought that he would be ideal, and was therefore somewhat taken aback when he met Worthington. The actor had bulked up considerably for his roles in Avatar (2009) and Terminator Salvation (2009).
A replica of the owl Bubo, used in Clash of the Titans (1981), was used for this film. Sam Worthington hated it, and threatened to destroy it when Louis Leterrier wasn't looking. According to Leterrier, "Worthington would say: 'This is ridiculous! This is a ridiculous thing to have in the movie! You're going to ruin my career with that owl!'"
Liam Cunningham, Rory McCann, Ian Whyte, and Alexander Siddig all appeared in Game of Thrones. Liam as Ser Davos Seaworth, Rory as Sandor "The Hound" Clegane, Ian as Gregore "The Mountain" Clegane/White Walker/Wun Wun, and Alexander as Doran Martell.
Despite the mythological nature of this film, it draws heavily on actual Minoan (Crete, approx. 2700-1450 BC) archeology for its props and costuming. The characters' long, curled hair is seen in palace frescoes from Knossos and other sites. The tiered dresses of the dancing girls in Argos' palace are PG-13 versions of the Snake Goddess figurines' costumes from the same palace site. With Andromeda's final costume, a nearly perfect replica of the Bee Pendant from Malia graces her neck; the only difference is that the movie version is constructed from silver rather than the original gold.
The Kraken was supposed to be the last of its kind, according to the mythology of this movie. The Kraken did not originate in Greek mythology. In the original story, Andromeda is menaced by a monster known as Cetus.
While the film is primarily based on Greco-Roman mythology, aspects of it are drawn from other cultures. The Kraken comes from Norse mythology, and the Djinn originated in the Arabian/Oriental regions, while Cepheus' snipe about Andromeda being a missionary, might hint at the coming Christianity (Christians often serve as missionaries).
Louis Leterrier originally wanted to make the film in 3-D, but Warner Brothers nixed the idea, as it was too expensive. After the success of Avatar (2009), the studio reconsidered. At this stage, however, most of the filming had been done, so the 3-D conversion was a retrofit.
Alexander Siddig (Hermes) was very dismissive of the film in an interview with the AV Club in 2015. He said sarcastically, "Oh, yeah. One of my finest. One. Of. My. Finest. Roles. I have so many stories about that experience that I don't even know where to start." After he burst out laughing, he continued by saying, "That was possibly the lamest movie I've ever been in. I mean, you know, there's some times when you do duds, and I must've been rubbish, because I think there was all of one minute more of performance that I may have done that didn't end up in the movie. So fifty percent of my performance was cut, and...yeah, there's not much you can say about that."
The thirteenth film released in select D-BOX enabled cinemas, located in the U.S. and Canada. In D-BOX's words, the motion control technology "adds to the movie's plot and underlying themes of fear, terror, and explosive action, by offering realistic sensations during most of the film's action scenes."
Early in the movie, Perseus told Draco that he would not use anything from the gods, but later in the movie, when he mets Zeus for the first time, Perseus accepts the gold coin from Zeus, that he used as payment for the ferryman.
Both this adaptation and the original contain actors from the Harry Potter movies; Maggie Smith (Professor McGonagall) plays Thetis in the original and Ralph Fiennes (Lord Voldemort) plays Hades in this version
Mads Mikkelsen and Gemma Arterton both previously starred opposite Daniel Craig in the James Bond films Casino Royale (2006) and Quantum of Solace (2008). Mikkelsen played Le Chiffre and Arterton played Strawberry Fields. Ralph Fiennes later starred in the James Bond film Skyfall (2012) as Gareth Mallory, who is promoted as M at the end of the film, and Fiennes returned in the role for Spectre (2015). Rosamund Pike, who played Miranda Frost in Die Another Day (2002), assumed the role of Andromeda in Wrath of the Titans (2012).
Following the tragic death of Liam Neeson's wife, Natasha Richardson, for his first public appearance, Neeson was accompanied by his good friend Ralph Fiennes at the Broadway premiere of "Mary Stuart". This was just before filming on "Clash of the Titans" began.
The trivia items below may give away important plot points.
According to Louis Leterrier, the movie was meant to end with Perseus and Andromeda ending up together (as in all previous tellings of the Perseus story) with Perseus and Io's relationship being purely platonic. However, the studio disliked this idea, and the movie was re-shot to have Perseus and Io end up together.
When Acrisius is disfigured, he takes the new name of Calibos. Calibos was a character who first appeared in Clash of the Titans (1981). He is named for Caliban, the antagonist of William Shakespeare's play The Tempest (1611).
In Greek mythology, Perseus and Andromeda had seven sons, one of whom is Perses, who became an ancestor of the emperors of Persia, and from whose name "Persia" is supposedly derived. Io (who in Greek mythology, is Perseus' great-great-great-great-great-great-great-grandmother) is portrayed by Gemma Arterton, who appeared in Prince of Persia: The Sands of Time (2010), as the love interest of a Persian prince.
Gemma Arterton was unable to return as Io for the sequel Wraith of the Titans (2012), because she was committed to Hansel & Gretel: Witch Hunters (2013). The script was re-written, and it was written into the film that Io died, and Perseus decided not to have Zeus resurrect her again.