"Unity Based on Actor Appearance Deception" (or "UBAAD"), is the false presumption that two characters are connected because they are played by the same actor.
It is impossible that the characters in-universe share the same perspective as we the viewers. We as the audience see the actress playing both Sister Jude and Elsa. In the context of the show, the characters simply see two different people who are not related. It requires a lot more suspension of disbelief. The two women have COMPLETELY irreconcilable back-stories, and no amount of playing with the timeline can have Elsa growing back her legs to become Sister Jude.
There are lots of television universes where the same actor plays completely unrelated characters and the in-universe characters don't notice. In addition, we have multiple actors playing two nearly identical characters that are probably one and the same, and two actors (Frances Conroy and Alexandra Breckenridge) who are absolutely playing the same character but from different perspectives.
So, when crafting your theories: be aware of this deception, lest you fall into the UBAAD trap.
- Cases in point from other series
- Mark Lenard played Sarek (an iconic Vulcan), a Romulan, and a Klingon in Star Trek. Jeffrey Combs has played nine different onscreen roles in the Star Trek universe. Garret Dillahunt played Jack McCall and Francis Wolcott, who were completely unrelated. The Twilight Zone recycled them all the time, as do all of the Law & Order series.