|“||(Goldar: No offense, boss, but they might find you a little disgusting.) Ivan Ooze: Well, I suppose you be the experts on that. You forget, I am a master of disguise.||„|
|~ Ivan Ooze to Goldar about his mastery of disguise.|
A Master of Disguise is a character who can be anybody during the course of the story. Giving a character this power and concealing its use from the audience for a "reveal" is very hard to pull off.
They may rely on extensive training and a vast collection of wigs, clothing and stage makeup to pull off the fakery. Or, their powers could be Phlebotinum-driven, in that they have the physical ability to alter their very shape and size to perfectly match that of the person they are duplicating.
Expect them to be called "The Chameleon" (even if real chameleons cannot hide themselves) and to be crucial to an "Impossible Mission".
Their allegiances can go either way. Sometimes they are villains, sometimes they are heroes (though not usually The Big Bad or The Hero themselves), and very often they're just Wild Cards.
See also Convenient Color Change; Latex Perfection; Master of Illusion; Shapeshifting; Wig, Dress, Accent; We Will Not Use Stage Makeup In The Future; The Power of Acting. Compare Clark Kenting. Master Actor is a subtrope that covers only the acting. Man of a Thousand Faces is when an Actor is a Master of Disguise. Someone may be Cast as a Mask.
Not all villains go as themselves through the entire work of fiction, some of them go in another form (or alter-ego) to hide their identity.
Please note that (A) this should not be confused with Happy Madison Production's The Master of Disguise and that (B) Black Hat refers to this technique as "the Skinwalker".