"Peri" (full name Perpugilliam, a name she rarely used) Brown was an American college student turned companion of the Doctor during his fifth and sixth incarnations.
If a medium is not mentioned, then this incarnation did not have companions who were original to that medium; it does not mean that this Doctor failed to appear in that medium.
The Sixth Doctor's companions from stage plays are difficult to assert with certainty, as different actors played the Doctor in the same play. If a medium is not mentioned, then this incarnation did not have companions who were original to that medium; it does not mean that this Doctor failed to appear in that medium.
