Half-Dopple (5e Subrace)
From D&D Wiki
This Subrace allows the crossbreeding of races without the use of dedicated halfbreed races. A half-dopple person is the child of a doppelganger father, born to a mother from some other race. This is extremely rare, as pairings almost always produce full doppelgangers. Half-dopples do not necessarily tend toward any specific sort of behavior, though many do wind up using their powers irresponsibly. Physically, they look almost indistinguishable, though their features may be slightly softer or smoother than usual- like a wax figure melting very slightly in the sun.
Ability Score Increase. You Charisma score increases by 1.
Shapechanger. You can use your action to assume the shape of another Humanoid creature no larger than yourself and no less than one size smaller than yourself. You can only impersonate creatures you have seen; you can't just make up new forms. This assumed form is visually flawless, but social interactions with you may reveal your impersonation if you fail to imitate the person effectively in front of people who knew them. You do not gain any racial traits, abilities, or skills by assuming another form, it is purely cosmetic. (The exception is movement features derived from physical anatomy. For instance, if you take the form of a humanoid with webbed fingers and toes, you would likely gain a swim speed. However, because such a form is not natural for you, your special movement speed is 5ft slower than that of the creature you are copying.) Assuming the form of the opposite gender does not grant the ability to reproduce as the opposite gender. This effect lasts a number of hours equal to your level. It can be used a number of times equal to half your level, minimum of 1. Your usages of this trait are restored after a long rest.
Sense Thoughts. Although not as potent as a full doppelganger, you did gain some psychic power. You can automatically and passively sense thoughts within 60ft of yourself. You cannot discern any thoughts or memories in particular- only that something is thinking and its general proximity and direction. This effect is only blocked by a barrier of 3ft of wood/soil, 2ft of stone, 2in of metal, or a thin sheet of lead. It does not sense undead or constructs, as their minds operate without psychic effects.