The Juggernaut is a major villain in most X-Men continuities. He is the brother of Professor Charles Xavier and a member of the Brotherhood of Mutants. He originaly possesed a dormant X-Gene but used mysticism to reawaken it, making him invincible. In some continuities he joins forces with the X-Men to fight the common enemy.
In recent years, he has become famous due to the online parody cartoon, "I'm the Juggernaut, Bitch!" This became so famous that the line was written into the third movie after it was already past the shooting phase.