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Jean Grey, the Phoenix... she finds a way to reincarnate herself constantly, so one never knows.

"Hugh Jackman Says 'The Wolverine' Features A Previous 'X-Men' Character, Christoph Waltz Might Appear in 'The Muppets 2' After All" by Charlie Schmidlin, www.indiewire.com. December 27, 2012.
Jean Grey, the Phoenix... she finds a way to reincarnate herself constantly, so one never knows.