- “My parents are the greatest superheroes on the planet. Everybody expects greatness from me.”
- ―Will Stronghold
William Theodore "Will" Stronghold is the main protagonist in Sky High, as well as the narrator of the film's opening and ending. He is the son of a famous superhero couple, the Commander and Jetstream, but doesn't seem to have inherited any powers until mid-film. He is played by Michael Angarano.
Will is depicted as a loyal and kind person, who values friendship and family more than pride of being a superhero. In the beginning of the film, he was completely distraught by the possibility that he may never inherit any powers, as a nurse discussed some rare cases whereas the child of two super-powered parents might never acquire any of their powers though they might activate later. He taps into his dormant power of super-strength when his arch-enemy, Warren Peace, threatens to attack his friends, forcing him to unleash the hero within; although this comes as a shock, he is overly excited by his new powers.
His popularity status escalates greatly after this, but also at the cost of his friendship to Layla, Magenta, Zach and Ethan. In the end, he puts friendship over pride and apologizes to his friends for his behavior. His partnership with Warren Peace eventually allows them to develop a close friendship, and his friendship with Layla escalates into a romantic relationship.
Will is starting his first day at Sky High: an institution that teaches future superheroes how to use their powers as well as the values and techniques of saving the world. Because he hasn't inherited any powers yet, he is assigned into the Sidekick Class; also known as "Hero Support". In the nurse's office, he hears that there have been cases where children of two super-powered parents never inherit any of their powers unless they fall into a vat of toxic waste or get bitten by radioactive insects. In the coming months, he begins to find new friends in his class.
When the school's bullies, Lash and Speed, trip him, he accidentally drops his tray of food on Warren Peace, the child of the villain that his father arrested years ago. Warren attacks him with fire, and when he threatens to attack his friends, Will lifts the table with little effort, inheriting his father's super-strength. His newly found power makes the school board reconsider his class status and transfer him to the Hero Class (which is similar to Honor Classe), where he becomes lab partners with student body president, Gwen Grayson, whom he also begins a relationship. Winning the Save the Citizen game with Warren against Lash and Speed, his popularity escalates several steps. After this, his friendship with Layla begins to falter, and Layla asks Warren to homecoming in order to make him jealous.
While having a party orchestrated by Gwen at his house, he brings her into the Secret Sanctum and Speed steals a gun called "The Pacifier" while they make out. Right afterwards, Layla crashes the party and Gwen tells her off, telling her that she is embarrassing herself in front of Will. Will, unaware of what they said, becomes confused with Layla's sudden change of attitude and interrogates Gwen, and when he finds out what she said, he dumps her the night before homecoming. While staying home to skip the dance, he looks over his father's yearbook and discovers a young student looking exactly like Gwen and sees the Pacifier; then notices that the gun has been stolen during the party. As Gwen reveals herself as Royal Pain and turns everyone into babies, Will makes his way to Sky High where he meets the escaped Layla, Warren, Ethan, Magenta and Zach, who fill him in on the story.
He apologizes to his friends for his behavior and kisses Layla before being interrupted by Gwen's lackeys. He goes to find Gwen while the others fight on their own. While confronting Gwen, he finds out that she is not Royal Pain's daughter, but really Royal Pain herself (because she was turned into a baby 20 years ago when the Pacifier exploded in a battle against his parents). The two begin to fight until Will gets thrown off the Sky High platform, but also discovers his second power: flight. He defeats Gwen with this power and saves the school before it crashes on Earth (with large help from Magenta). Afterwards, the babies were reverted into their real ages and Gwen got arrested. He is seen making out with Layla while floating outside the homecoming dance.
In the epilogue of the film, he narrates that compared to homecoming, the rest of the year became very boring; then jumps to Sky High's bus driver, Ron Wilson, who has gotten his powers after falling into a vat of toxic waste and begins to defend the city from giant robots; and then explains that his girlfriend became his arch enemy; his arch enemy became his best friend; and his best friend became his girlfriend.
- Superhuman Strength: Will inherited superhuman strength from his father as he was seen throwing Warren through a wall into a pillar and tossing Royal Pain around.
- Invulnerability: Will's father possesses the power of invulnerability; so it's fair to assume that Will possesses the same power. This is also some evidence that he has this; for example when he was used as a battering ram by Royal Pain and he seemed to not recieve any significant or severe injury. When fighting Warren as well; Will showed no sign of physical injury or burns.
- Supersonic Flight: Will possess the power to fly which he inherited from his mother when surprising Royal Pain (and himself) after falling through a window.
- When visiting the nurse, Nurse Spex stated that if a child has two biological superpower parents its unknown if they will have powers, until Will proves that a child will both have superpowers from their mother and father.
- Will is the first and only one to prove that a child will have superpowers from their parents.
- Will is the first person to have three superpowers.
Characters: Will Stronghold | Layla Williams | The Commander | Jetstream | Warren Peace | Ethan | Magenta | Zach | Royal Pain/Gwen Grayson | Lash | Speed | Penny Lent | Stitches | All American Boy | Coach Boomer | Ron Wilson | Principal Powers | Professor Medulla | Nurse Spex | Jennie Elast | Mr & Mrs Timmerman
Locations: Sky High School | The Stronghold's House