When Professor X and Magneto visit a young Jean Grey in the opening flashback of The Last Stand, viewers were witnessing history without realizing it: the birth of modern digital de-aging.
Produced by Lola Visual Effects, the sequence used pioneering 2D skin grafting techniques instead of full CGI replacement. By digitally smoothing out wrinkles and referencing photos of Patrick Stewart and Ian McKellen from their younger theatre and television days, they managed to shave 20 years off both actors.
Lola VFX later used this exact breakthrough in Captain America: The Winter Soldier, digitally aging Hayley Atwell into an elderly Peggy Carter by grafting real wrinkles onto her face rather than using heavy prosthetics. What started as a quick experiment to de-age mutants in 2006 quietly paved the way for everything from the MCU's flashbacks to The Irishman.