Technically, Nyssa from the Fouth (and later Fifth) Doctor's era, who wasn't originally planned to be a companion, but got turned into one anyway. However, she became a permanent character in the story immediately after her introduction, instead of a season apart as with Donna. I think Harry Sullivan was also mentioned a few times - though not actually seen - as being UNIT's staff doctor before he showed up in person during the Fourth Doctor's debut.Havok wrote:Other than Donna, has there ever been a recast of a companion from a one off episode character?
It would have happened with Freema Agyeman's character from "Army of Ghosts," if not for the fact that she was killed off at the end of that episode and RTD didn't fall in love with the idea of Agyeman as the next companion until it was too late to do a rewrite, resulting in Martha giving that extremely half-arsed "by the way, I used to have a physically identical cousin!" explanation when she eventually showed up.