Unlikely Spare

Marge: And my necklace!
Homer: Ehh, that's no big loss.
Marge: Homer, that necklace was a priceless Bouvier family heirloom.
Homer: Oh, you've probably got a whole drawer full of 'em.
Marge: Well, yes I do. But they're all heirlooms, too.

—The Simpsons

There are some characters that care so much about their clothing/a particular item that they will pull out extras if necessary. This generally occurs at the most unlikely times. Spare glasses appear from nowhere in the middle of a fight or uniforms/outfits are replaced on the fly. Fights will even pause for this to occur.

It is most noticeable when another person (or even the person doing so) comments on it.

Related to Crazy Prepared. Can be applyed to Beauty Is Never Tarnished.

Examples of Unlikely Spare include:

Anime and Manga

Bleach: Ishida pulls out a uniform from his backpack, says "Good thing I brought a spare," and Orihime asks why he brought it.
- While it's reasonable he'd have packed clothes (even in the original plan they expected to be spending a few days away from home), he brought a spare cape. ...Which brings up again that he's wearing a cape.
In Busou Renkin, Papillon always seems to have an extra mask hidden in his speedos.
In Sayonara, Zetsubou-sensei, after Meru's trolling of the class with abusive messages is temporarily stopped when her phone runs out of power, she just opens her shirt, revealing several phones strapped to her chest. The protagonist compares her to Rambo.

Comic Books

Comically averted in Spider-Man vs. Wolverine. Peter Parker not only didn't have a spare, but he didn't even have his regular suit with him (he was in East Germany on assignment for the Bugle).
- He ended up buying a not very authentic Spider-Man costume from a tailor whose son was going to use it for a costume party.
* In the Sonic & Knuckles comic, Knuckles had a spare Chaos Emerald, which he used to keep Angel Island afloat. He broke the first one to keep Robotnik from getting it, then brought out the spare after he left. Granted, Chaos Emeralds are far more common in the comic than in the games, but it's not exactly something you trip over.
- While Knuckles does get another Chaos Emerald in another comic, the one he smashed in the Sonic&Knuckles special was just a fake. Sonic didn't see him make the switch, but neither did Robotnik...

Film

Rat Race: After Merrill angrily smashes her phone after yelling at one of her workers, she tells Vera that she "carries extras".
In Sky High, super strong hero The Commander, when told his son was designated a sidekick, goes to angrily call the school to complain, only to crush the phone when he angrily pushes the buttons. He then opens a kitchen drawer which has several extra phones and starts dialing again.
In Brain Donors, Jacques routinely smashes his alarm clock into pieces when it wakes him -- and has a closet full of new alarm clocks to replace the ones he destroys.

Live-Action TV

The clothes on Gilligan's Island. Gilligan, the Skipper and Hinkley wear the same clothes every day but Ginger, Mary Anne and the Howells apparently packed trunk after trunk of different (and, for Ginger and the Howells, fabulous) clothes for their three-hour tour.
Subversion: In an early episode of Married... with Children, the local mall stops selling Peggy's bras, so Al goes out of town and buys enough backups for years.

Video Games

Edgeworth in the Ace Attorney games replaces his silk cravat after someone cries and wipes her nose on them in the latest game.
- Also Adrian and her glasses. Whenever she's thoroughly shocked, her glasses shatter, and she immediately pulls out a spare. It's certainly normal to have spare glasses, but about four pairs of her glasses ended up shattering, far more than the number of glasses most people carry around with them. Or generally own at a time.
In Final Fantasy VII: Advent Children, Rude pulls a second pair of Cool Shades out of his pocket when the pair he's wearing are broken. Fanon holds that he has a Sunglasses Maker Materia in his pocket.

Web Original

Kamina in Double K keeps at least three pairs of his trademark Cool Shades on his person at all times.
In Dead Winter, Black Monday Blues has spare sunglasses.
In The Horribly Slow Murderer With the Extremely Inefficient Weapon, the killer is slowly beating his victim to death with a spoon. Eventually, the spoon breaks and the victim breathes a sigh of relief. At this point, the killer opens his jacket and reveals numerous identical spoons strapped to his chest.

Western Animation

In Hey Arnold!, Arnold loses his grandfather's antique watch. He has to go down into the sewers to retrieve it, where he has to face swarms of rats and the Sewer King. After he finally gets the watch back, it turns out his grandfather had a spare watch all along.
In The Simpsons episode mentioned above, Marge's necklace is stolen. She is later shown to have a huge ball of identical necklaces from which she pulls another one.
- In another episode, Homer accidentally squirts chocolate onto Tom Wolfe's trademark white suit. Wolfe simply tears off the dirty suit to reveal an identical one underneath.
In the My Little Pony Friendship Is Magic episode "Dragonshy", an avalanche leaves the group covered in dust, ruining Rarity's scarf. She pulls another one out of her saddlebags.

Rarity: This is why a girl always packs extra accessories.