Puffer Fish

Pufferfish, also known as puffers, balloonfish, or blowfish, are well known to swell up into a ball-like shape as a defense mechanism in order to appear larger and scare away predators. They also have Spikes of Doom to go along with it.

Some pufferfish also have the added bonus of being pretty damn poisonous to go with it. The majority of their bodies are steeped in toxin, and if you were to eat one, you'd die pretty dang quickly. Course, in places like Japan where people consider them a delicacy, professional chefs have to be extremely careful in cooking them.

Literature

 * In Discworld, the Bloat blowfish is ridiculously poisonous, making it a favorite weapon of some professional assassins. - its "puffing" mechanism seems to be chemically based so if you get stabbed by something covered with its poison (or eat one - unless prepared by an expert), you will... puff. They say after blowfish poison is used, you don't need to remove the body, merely repaint the room.

Live Action Television

 * On Enterprise, Dr. Phlox's species have a reflexive ability to inflate their heads when threatened, in a manner similar to a puffer fish expanding its body.
 * The Columbo episode ''Murder Under Glass" centers around the killer- a trained chef- using blowfish poison to kill a victim. Columbo is tipped off to the exact poison and method later in the film when the killer is serving fugu sashimi and is revealed to be licensed and trained to prepare the fish.

Video Games

 * Super Mario Bros: Puffer-Cheeps (Mario & Luigi), Cheep-Cheep Pufferfish (Mario Pinball Land), Porcu-Puffer (Super Mario World and New Super Mario Bros Wii) and Spike Bass (New Super Mario Bros).
 * Mega Man X has the Gulpfer enemy, which sucks in water and in the process attempts to swallow X whole.
 * Puffer fish mecha also appeared in Mega Man Zero 4. They exploded into spikes if left long enough.
 * Puftup from Donkey Kong Country 2
 * Puftoss from Donkey Kong 64
 * Swellbelly in Banjo-Tooie
 * Qwilfish from Pokémon
 * Sonic 3 has these in Marble Garden Zone. And a fair few more in the series.
 * Crash Bandicoot 3: Warped has pufferfish enemies in the underwater levels.
 * Appear as a type of Chest Monster in Ecco the Dolphin, appearing in the midst of schools of otherwise-tasty fish. They're actually safe to eat if you can catch them un-puffed.
 * One serves as a boss in the SNES version of Parodius Da! It continues to inflate until it fills the entire screen.
 * The game Feeding Frenzy includes puffer fish, which can only be eaten when unpuffed; trying to eat a puffed one just causes you to bounce off and lose points.

Western Animation

 * Uncle uses one in Jackie Chan Adventures in order to cast spells.
 * Mrs. Puff from Spongebob SquarePants
 * Bloat from Finding Nemo
 * The manager of the Whale Wash from Shark Tale was a puffer fish that blew up when scared.
 * The Simpsons: Homer Simpson's one and only exposure to sushi ended with a cut of fugu (pufferfish) prepared by an apprentice sushi chef. Dr. Hibbert said he would die in 24 hours,
 * Duck Dodgers: in the episode "Samurai Quack", it goes one step further that he doesn't eat poorly prepared sushi....he takes a big bite out a whole and totally unprepared Blowfish after slapping it for a bit Mushroom Samba.
 * "...and let that blowfish blow!"