Chris Hemsworth
Australian actor Chris Hemsworth plays the titular Thor, an all-powerful being from Norse mythology. Thor has superstrength and the ability to summon lightning to use as a weapon against his enemies. To look the part of a powerful god with unspeakable power, Hemsworth went through an intensive, six-month-long training regimen. For the role, he ate "non-stop," started lifting weights, and ultimately gained 20 pounds of muscle.
Hemsworth was initially not director Kenneth Branagh and Marvel Studios guru Kevin Fiege's first choice for the role. After an extensive search, Hemsworth was initially denied the role but was later given another opportunity to audition for it. The rest, as they say, is history, as Hemsworth went on to play the character in eight additional films in the Marvel universe.
At the beginning of the film, Thor is a brash and arrogant man who doesn't fully appreciate the gravity of his power. However, after he is stripped of his powers by King Odin, he is forced to become human and confront his own foibles. While human, he also has to contend with his brother, Loki, who presents him with a challenge as Loki works to take control of the Kingdom of Asgard.
In the end, despite his violence and weakening arrogance, Thor learns humility and the importance of helping other people in times of need. He starts to adapt human characteristics, allowing him to defeat Loki, the Frost Giants, and all those who wish to do Asgard harm.
Natalie Portman
Natalie Portman plays Jane Foster, whom Thor finds after being transported to New Mexico in the United States by his father as a form of punishment. She is an intelligent, brash young woman who has an innate curiosity about the universe, which led her to become an astrophysicist. After meeting and starting a romantic relationship with Thor, her horizons are broadened.
Portman was offered and accepted the role before work began on its script. She wanted to work with director Kenneth Branagh and wanted to be involved in building a character from the ground up. She saw playing Foster as a way to give credit to female scientists of old who weren't given credit for their discoveries because of their gender. She wanted Foster to be a bold, independent character who was willing to take risks whenever it was called for. Ultimately, she wanted Foster to become a role model for young women wanting to join STEM fields.
Tom Hiddleston
Tom Hiddleston plays Loki, Thor's mischievous, trickster adopted brother who is bent on controlling the world and taking control of his adoptive father's throne in Asgard. Initially, Hiddleston (who had a preexisting relationship with Branagh after working with him in two stage plays) auditioned to play Thor. However, after going through the audition process, Branagh decided Hiddleston would be better suited to playing Loki, who he wanted to be a "nastier" version of King Lear and "lean and hungry."
Like Chris Hemsworth, Hiddleston prepared for several months before the start of filming. He modeled Loki after actor Peter O'Toole, who was known for playing complicated characters. And Loki is just that: complicated. He experiences no real character growth throughout the film but encounters countless roadblocks that prevent him from accomplishing his goal.
Anthony Hopkins
Anthony Hopkins plays King Odin, the leader of Asgard and Thor and Loki's father. Despite knowing nothing about the comics, Hopkins agreed to play King Odin because of his interest in Shakespeare and the relationship between fathers and sons. He also has some of Odin in himself, calling his character "hot-headed," "stern," and "purposeful," which is exemplified by his decision to banish Thor to the mortal world and strip him of his mortal powers to teach him a lesson.
