In most fictional universes (and
Real Life),
things tend to function in a particular, expected way, and perform that function consistently.
Phasers have settings,
guns will go off when the trigger is pulled (and sometimes when it isn't), healing potions will heal, and
cars will ignite as they fly through the air.
But sometimes the plot calls for an item to operate
in ways that weren't previously established.
This effect is unexpected, or even
inconsistent with its previous known functions. But it'll
get you through to the next plot point, and
that's all that counts.
When a writer attempts to explain the sudden change of behavior, he/she will frequently invoke
Phlebotinum Breakdown, or
Retcon the function into the item's repertoire. The way to tell, frequently, is watching to see
whether this new old function appears again.
If the change of function is not merely a handy means to an end, you may instead have
Chekhov's Gun—particularly if the characters notice or
should have noticed.
My Car Hates Me is a vehicle-specific subtrope, as
Context Sensitive Button is for control panels, and
Super Cell Reception is a phone-specific subtrope. The superhero version is
New Powers as the Plot Demands. Not to be confused with
Magic Tool and
Green Rocks, both of which are known from the outset to have multiple and possibly unknown functions or the
Green Lantern Ring which can explicitly do just about anything if you know how to use it. Remember, this is about a specific "normal" item acting strangely; do not add examples of all-purpose phlebotinum like Star Trek's "reverse shield polarity" and "deflector pulse" or Doctor Who's sonic screwdriver.
Examples
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Live Action TV
- In the 1979 TV series Salvage1, monohydrazine was used to solve any number of problems, from fueling a rocket to restarting oil wells.
- Star Trek's automatic doors will always open (when not locked) when a person approaches, and shut as the person moves away—unless the door NEEDS to be wide open, in which case...
- More to the point, the Main Deflector Array has been used to do just about everything.
- It's even the go to choice when you want to do a one shot overloaded weapon attack. It does more damage than the actual weapons would.
- The Stargate in the various Stargate series. Sometimes it closes just before someone "unwanted" is about to enter it and sometimes it allows them to go into the orifice. Sometimes it just stays on or closes for no apparent reason. It's a complete mess in what's otherwise a decent universe.
- The zat guns too, although in this case it may be a subversion since they just kind of lost an ability. The rule at the beginning of the TV series was: first hit stuns, second hit kills, third hit disintegrates. It was an excuse to get rid of any inconvenient bodies that they didn't want to keep track of. The creative team eventually decided it was stupid and the ability just kind of vanished. This was lampshaded in 100th episode Wormhole X-Treme!.
- Buffy the Vampire Slayer. Sunlight burns nameless mook vampires faster then the recurring ones.
- For that matter, Buffy can hit a Mook vampire anywhere in the torso and he'll turn to dust, staked through the heart. It's a plot point in Season 2 when a named vampire is shot with a crossbow bolt barely missing the heart, and it's *much* closer than it normally takes for Buffy to kill anyone.
- Classic example; time bombs will go faster or slower depending on how much tension is needed.
- The patients on House will get sicker or better depending on how much time is left in the episode.
Toys
Video Games
- Many of the gadgets in the Ratchet & Clank fit the bill. The Dynamo from R&C3 in particular can not only make solid platforms, but can also create a swing rope to use to jump between. The Electrolizer from R&C2 can fix nigh anything, with any technical fault, just by spinning a few dials to allow a current through. Anything from a hoverbike, to a computer terminal, to a Broken Bridge.
