X3: It is unknown how Jimmy came under the care of Worthington Laboratories, but when he did, Dr. Kavita Rao was able to create a permanent cure for mutations from his body. She was however, unable to synthesize what was taken from Leech, so he needed to live at their labs, but was taken care of and generally treated well. His hair was apparently shaven for hygienic reasons and was not part of his mutation. Beast, operating as Secretary of Mutant Affairs, visited Jimmy and approved of his use. When he approached Jimmy, Beast's hand turned back to human, then reverted when he moved away.
When Magneto learned that without Leech, the cure would no longer exist, he set out to kill the young mutant. During a raid on the labs, Juggernaut was sent to dispense with Leech, but Kitty Pryde followed him to save the boy. Kitty reached him first, but was unable to escape since Leech canceled out her powers. She then tricked Juggernaut into charging them, which canceled out the big man’s powers just before he ran into the wall, knocking himself out, and Kitty and Leech escaped through the holes he left in his wake. Leech, his hair growing back, then enrolled at Xavier’s School to learn how to control his powers.
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