Some TV programs have characters that aren’t played by actors – or anyone, really.

In the world of Frasier, a spinoff from storied US sitcom Cheers, the eponymous character’s sister-in-law Maris is the butt of many jokes from the show’s main characters, radio psychotherapist Dr Frasier Crane (Kelsey Grammar) and his equally snobby and uptight brother Niles (David Hyde Pearce).

Let’s face it: Niles might just be one of the more exacting, neurotic, and pretentious characters to have graced the small screen.

We can glean this from Niles’ tastes (opera, fine wine, Italian tailoring), and also his predilections, for instance how he orders his steak.

“Not so lean it lacks flavour,” he insists, “but not so fat that it leaves dripping on the plate … not true pink, but not a mauve either, bearing in the mind the slightest error either way and it’s ruined.”

We also learn a considerable amount about Niles from Maris and the manner in which the show’s characters observe and comment on her (despite, you know, her perpetual absence). Niles may be somewhat stuffy and difficult; Maris is impossibly insufferable.

In fact, Maris we are told, is “like the sun, but without the warmth”.

As domineering and demanding as she is, Maris also happens to be completely unseen – always. She is in fact what’s known in the business as an “unseen character”. Not only does the audience never see her nor hear her voice, no actor portrays Maris on the show.

The audience is in on the gag, of course. The absence of Maris is usually explained away because she’s resting in another room, recovering from an unusual malady, or otherwise preoccupied.

So why not have an actress playing the part? Evidently that was the original intention of the program’s showrunners. As time went on, however, and descriptions of Maris and her behaviour became increasingly ridiculous, not only did the part become harder to cast, it was more humorous not to.

“We felt it was better if she was left unseen,” says program co-creator Peter Casey. “It was much funnier adding new and outrageous descriptions.”

Perhaps in this instance it’s a case of the character viewers have constructed in their imaginations being far more memorable than one that might actually have been depicted. What the mind creates is more vivid than what a flesh-and-blood thespian could likely portray.

Consider the classic creature feature Jaws, which is extremely scary, almost unbearably so, until you eventually see the rubber animatronic shark created by the film’s special effects team, which dubbed the model “Bruce”, and which is about as scary as that name might suggest.

Unseen characters existed well before the Seattle-set Frasier. In the aforementioned Cheers, in fact, we often hear about Vera, long-suffering wife of corpulent bar denizen Norm Peterson (George Wendt), who is usually depicted dodging his wife’s phone calls.

But we never actually see Vera (well, there is one episode where an actress playing Vera appears, but her face is completely obscured, keeping the joke alive).

Deceptively perspicacious LA police detective Columbo (Peter Falk) caught perpetrators off guard by asking “just one more question” as he departed from an interview.

The trench-coat-attired sleuth regularly refers to “Mrs Columbo”, a supportive partner who features in the detective’s anecdotes.

From early episodes we are informed the lieutenant’s spouse provides him with a pencil every day, which he invariably manages to lose. So, we learn that Mrs Columbo (in the original Columbo we never learn her first name), considers her husband forgetful, and would prefer that he smoke a pipe rather than the cigars he favours. She’s also sceptical about his police skills.

Could our lead character have been making up these stories (and the wife who tells them) as part of a strategy to lull felons into a false sense of security? The stories, definitely, but the way in which the show unfolds would suggest we are meant to think Columbo’s spouse is real but simply hidden from view.

In Minder, dodgy and scheming second-hand car dealer Arthur Daley acts in a less-than-scrupulous manner, bending laws to suit his needs. But there is one authority he will not mess with, and that is his spouse, who he less-than-lovingly refers to as “’er Indoors”.

It’s a sign of how deeply the show resonated that ’er Indoors was officially entered into the Oxford English Dictionary of Modern Slang, where it is defined as “one’s wife or girlfriend, a domineering woman.”

Fond of malapropisms such as, “the world’s my lobster”, Arthur maintained that ‘er Indoors was the bane of his (somewhat disreputable) existence.

In Magnum PI, the titular character, Thomas Magnum (Tom Selleck), has the use of a guest house and Ferrari courtesy of the generous and enigmatic novelist Robin Masters. The luxury digs are part of an estate known as Robin’s Nest.

Mr Masters might be very elusive and not actually seen, but in early episodes audiences could clearly hear conversations estate manager Higgins (John Hillerman) was having with him over the phone and intercom. The voice heard in those conversations, which take place over half a dozen or so episodes, was none other than Hollywood titan Orson Welles, who in his later years did plenty of voice work, including for the Transformers franchise.

Unfortunately that means Magnum PI is more of a footnote than entry in this story.

Eventually the Frasier writers orchestrated a divorce for Niles and Maris, paving the way for the former to pursue his infatuation with his father Martin’s (John Mahoney) live-in carer, Daphne Moon (Jane Leeves).

And what of Maris? Well, she went from unseen to completely absent – from, ubiquitous and dominant (albeit invisible) to barely mentioned, and then forgotten. Fortunately, no actors lost their job in the process.