JEAN GREY

Jean Grey is now synonymous with telepathy, but the Marvel Girl who joined the team in X-Men Vol. 1 #1 (1963) had no telepathic power at all. Stan Lee and Jack Kirby introduced her with telekinesis alone — she levitated objects, hurled debris, and rearranged the battlefield, while every psychic feat in those early issues belonged to Professor Xavier.

The telepathy existed, but it was buried. Later stories established that Jean's psychic gift had erupted traumatically in childhood, and that Xavier had placed mental blocks on it while he trained her, judging the power too dangerous to hand to a teenager all at once. Only after years of schooling did he begin removing the barriers and letting the telepath emerge in stages.

The slow unlocking explains one of the strangest power curves in the early X-Men: the team's supposed lightweight kept gaining an entirely second mutation's worth of ability without any new origin event. What readers were watching was not a retcon-powered upgrade so much as a vault being opened one door at a time — the same vault the Phoenix would later blow off its hinges.