Sungkyunkwang Scandal- FL disguises herself as her brother.
Perfect Couple (2014)- FL takes the place of SFL because SFL doesn't want to marry the ML.
Beautiful Gong Shim- ML grew up with an adoptive father and has another name because he was kidnapped as a child. In reality he's a chaebol.
Black- ML is a grim reaper who takes over the body of a dead detective.
Blood- ML is secretly a vampire so he hides his true identity posing as a doctor.
Bpoop Phaeh Saniwaat- FL dies in the present but instead of going to the after life she travels to the past and takes over the body of another woman that died. She lives as her.
Healer- ML disguises himself as a clumsy journalist. In reality, he's a badass secret messenger/courier.
Love O2O- Both leads and many characters have alter egos in an online game.
Man to Man- ML is a government secret agent so he has many identities. It is such that his real name is never revealed.
Mirror of the Witch- FL is a princess with witch's powers but is raised ignorant of this as a commoner.
Moon Embracing the Sun- FL is the original crown princess and was engaged to the ML but the villains tried to kill her so she loses her memory and is raised as a shaman.
Moon Lovers: Scarlet Heart Ryeo- FL goes back in time and wakes up in the body of her past incarnation.
My Girl- FL poses as ML's long lost cousin.
Pinocchio- ML is raised as someone else. He lies that he lost his memory.
She Was Pretty- FL has her friend pose as her because she's ashamed of her looks and doesn't want ML to recognize her.
The Emperor: Owner of the Mask- ML is prince and later king but he hides his true identity behind a mask and later hides as a commoner while someone else takes his place as king.
The Eternal Love- FL travels back to the past and shares a body with another soul (original owner of the body).
The Legend of the Blue Sea- ML is a con artist so he has many different personas/disguises.