In a study of 18th-century French comedy, F. C. Green suggests that an “invisible character” can be defined as one who, though not seen, “influences the action of the play”. This definition, according to Green, would rule out a character like Laurent (Lawrence), Tartuffe's unseen valet, whose sole function is merely to give the playwright an opportunity to introduce Tartuffe.
I'm Sorry I Haven't a Clue: the scorers Samantha (or occasionally Sven) are regularly referred to but never appear. An empty chair is provided for them at recordings.
In the long-running British radio soap opera The Archers, a number of permanent inhabitants of the village in which the story is set are frequently referred to by name but are never heard from in their own voices. Fans of the programme often refer to these characters as "the silents".
In the radio comedy series "The Clitheroe Kid", Jimmy's friend Ozzie was frequently referred to but never heard in the shows.
On Will and Grace, Stan Walker, Karen Walker's incredibly wealthy, unfaithful, and morbidly obese husband, is never seen, although his wife and mistress fight over him and his estate.
On Frasier, Maris Crane, Niles Crane's wife, is not seen on camera in most episodes, but is often the subject of plotlines and jokes. Maris makes only two onscreen appearances, thus she is not an unseen character. One is in the episode "Voyage of the Damned" when her shadow is seen through a shower curtain (she is spoken to but makes no reply), and the other is in "Rooms with a View", where she appears in Niles' memory, almost completely covered by bandages after surgery.