Metamorphose

Metamorphose (肉体変化 (メタモルフォーゼ) ), also known as Metamorphosis in the Baka-Tsuki and Yen Press translations, is an esper ability that is purported to exist in Academy City. As it name states, it is a power that allows the user to change their appearance.

Principles
According to Etzali, the ability allows someone to have a face or body similar to others, though it is apparently impossible to change in a genetic level. It is probably similar to Aztec's magic, which uses the flaying of skin to use a disguise.

Tsukuyomi Komoe references that said ability is rare, and that only three espers in the whole of Academy City have that ability.

Kamijou Arc
When faced with the other Touma, Misaka Mikoto considered Metamorphose as a possibility.