Dead End Job

In most ongoing series, there are several job positions that need to be filled. Often, these roles will be filled by the characters of a Five-Man Band. But in some series, there is one specific job that tends to have a high turn-over rate. This allows the author to keep bringing in new characters who have skills useful to that particular story or who can betray the operation from the inside.

When played straight, these positions become an obvious Chekhov's Gun; whoever the "new guy" is, everyone knows that they will become significant later on. However, this character can still turn out to be no more or less relevant than anyone else.

The nature of this job lets the writers kill this character off, if they want to, usually in some emotionally significant way. Retirony may come into play. Characters in Dead End Jobs do tend to hang around long enough for viewers to get attached, Chekhov's Gunman or not.

When done poorly, the audience may start wondering why the HR department doesn't get rid of the job altogether and delegate that work to established and trustworthy characters.

Please note that this trope does not apply to Red Shirt characters of the type you tend to find on Star Trek. Characters who hold jobs of this type tend to last for a full plot arc, be significant to that plot arc, and then get conveniently shuffled off-screen at the end to make room for the next plot-significant character.

A sub-trope of High Turnover Rate.

Examples of Dead End Job include:

Film

This Is Spinal Tap has a running gag where the band's drummers keep dying in improbable ways, to the point that when their keyboard player dies, they find out that he used to be a drummer.
Two of the four Three Stooges "Third" Stooges died during the run of the series.

Literature

The job of Defense Against the Dark Arts in the Harry Potter series. In seven books, they go through seven professors, and every one of them is significant to the plot. Dumbledore even lampshades this at one point. As it turns out, Voldemort had cursed the job so that no one who got it could hold it for more than a year, and this persisted until his death.
In The Sookie Stackhouse Mysteries, there are two jobs like this. One is that of short-order cook at Merlotte's, and the other is that of bartender at Fangtasia.
The Bastard Operator From Hell series has the post of Systems Supervisor as this, with said supervisor being killed off by the BOFH or the PFY once they become too dangerous. Whether or not this can also be said for the Director of IT post is debatable.
In one of Isaac Asimov's Azazel stories, the first head of the Committee on Diminishing Returns lasts thirty-two years, the next one sixteen, the next one eight... After the sixth, they decide the Committee's name must be unlucky, and a change is in order. It works.

Live Action TV

Number 2 in The Prisoner.
They went through three "sassy southern" waitresses on Alice.
Charlie's Angels did this to an extent:
- Jacklyn Smith as Kelly Rogers lasted the entire series
- Farah Fawcett-Majors as Jill Monroe, replaced by Cheryl Ladd as Kris Monroe
- Kate Jackson as Sabrina Duncan, replaced by Shelley Hack as Tiffany Welles, replaced by Tanya Roberts as Julie Rogers (at which point Charlie stopped hiring former female cops and started hiring former female models)
Three's Company likewise went through three different Ditzes (one of which wasn't all that ditzy).
Night Court had a problem hanging on to female baliffs.
- Selma Diamond as Selma (who died in Real Life)
- Florence Halop as Florence (ditto)
- Marsha Warfield as Roz (who AIR developed diabetes and almost died)

Web Comics

The position of explosives expert in Tagon's Toughs in Schlock Mercenary has a relatively high turnover rate: So far it's killed at least two Mauve Shirts who have held it (Kevyn, their unofficial expert, has also died repeatedly). Many of the grunts believe the position to be cursed, although its current holder doesn't seem too fussed.

Western Animation

Dilbert illustrated the corporate version of this trope with The Bungee Boss.
South Park's constant killing of Kenny is a parody of this trope, although being as Kenny continues to be a cast member, ultimately is an aversion.