Board Thread:The Panopticon/@comment-26285319-20170104192003/@comment-26845762-20170304190252

My definition of spin-off would be "a story/series published without the Doctor Who logo with characters from a story published with the Doctor Who logo". The Iris Wildthyme series is a spinoff; BBC Eighth Doctor Adventures, BBC Past Doctor Adventures, and Big Finish are not.

Senor 105 appeared in a few Iris Wildthyme stories, but no Doctor Who stories. His series is a "spinoff of a spinoff". (well, aside from that one on Venus)