Impersonation, simulation, alternate universes and general xeno- and techno-shenanigans are a mainstay of the Star Trek franchises.
It occurred to me that I can't really think of a main character who was not subject to:
- recreation on a holodeck
- impersonation by aliens
- depiction in the Mirror Universe or another parallel universe
TNG has most characters excluded in "Parallels". DS9 has most characters excluded by its five Mirror Universe episodes, not to mention the Changelings. Voyager had an entire ship and crew impersonated in "Course: Oblivion". Most of Enterprise is covered by "These Are The Voyages". And many characters in Discovery have been depicted in their Mirror Universe forms.
Who is the most recurring character who has always been themselves?
In order to disambiguate, I'm going to consider "not being oneself" to mean we never saw cases where:
- It looked like character X, but wasn't actually "the real" character X, or
- It looked like character X and was the body of character X, but X wasn't in control, or
- Character X assumed the role of character Y, or,
- The usual appearance of X is not the true appearance of X to begin with.
- X was sufficiently disembodied or re-embodied. (Turning into a lizard or an energy field or de-aging by 30 years)
Just in case it's not clear, in-universe pictures, viewscreen depictions, holographic communication technology, etc do not count as not being oneself.
In case of ambiguity about whether a particular situation counts or not, please ask for clarification in the comments or chat, and I'll try to hone the question.