Romana (Doctor Who)
Romana II appeared pseudonymously in a series of audio plays produced in the early 2000s by BBV. In this series, Lalla Ward played a character who appeared with K-9 in an unnamed parallel universe.  This character is called the Mistress (which was what K-9 called Romana in the television series).  Because of an unusual copyright situation in which BBV was able to license K-9 but not Romana or other Doctor Who elements, the Mistress is not explicitly called Romana.  For similar reasons, the parallel universe (obviously intended to reflect Romana's exile in E-Space) is called a "pocket universe" in the series' packaging.