Forget Magneto: This X-Men Villain's Helmet Blocked Xavier's Power Way Before The Movie
There's been a lot of talk recently about Magneto's (Ian McKellen) helmet in the first "X-Men" movie after screenwriter David Hayter confirmed the cinematic logic behind wearing the signature costume element in the film. Yes, it turns out that the reason Magneto's helmet blocks Professor X's (Patrick Stewart) psychic waves is that otherwise, Charles Xavier could defeat his nemesis relatively easily, simply by attacking his mind and putting him to sleep.
While this element was not found in the X-Men source material (though it quickly found its way into Marvel's comic book continuity after the movie's release), it does have its roots in another of the franchise's signature villains. Juggernaut is a hulking behemoth who also wears a helmet, and his headgear was the first to be used to block Professor X's attacks, a point that has been explored in the pages of Marvel Comics more than once.
In fact, one of the most effective ways for Juggernaut to be defeated in Marvel Comics lore is for him to have his helmet removed. This leaves him open to Xavier's psychic attacks and allows the team's creator and leader to subdue the nigh-unstoppable foe with very little collateral damage. However, there's also a unique connection between the two characters that helps to explain their ongoing animosity.
Professor X and Juggernaut have a long history
As any major "X-Men" fan knows, Charles Xavier is actually the stepbrother of Cain Marko. The two became part of the same family unit when Cain's father, Kurt Marko, married Charles' mother, Sharon. Years later, the two step-siblings would deploy and serve together in the Korean War, which led to Cain discovering a cave dedicated to the mystical entity Cyttorak.
This is how the Juggernaut gains the muscle and massive size that have since become trademarks of the character. As for his hatred for his younger stepbrother, Charles, that is explained by the childhood that the two shared after their parents were married.
After the wedding, Cain's father, Kurt, begins to favor Charles over his own son, regularly mistreating and even abusing Cain as a result. This causes Cain to begin bullying Charles and helps to explain the close connection and familiarity between the two foundational X-Men characters. Furthermore, it helps to demonstrate why Juggernaut understands Charles' powers so well.
In more recent times, the X-Men villain has also acquired a telepathy-blocking skullcap, which he uses as a secondary shield in case his helmet is removed. Though Magneto's headgear change for the movie was in response to a plot hole, it's entirely possible, though it's never been confirmed, that the idea sprang from the film's writers being familiar with Juggernaut's comic book history.