Scraplets

Scraplets are the name of several fictional characters and an alien race in the various Transformers universes.

Transformers: Generation 1
Scraplets are robotic parasites. They are semi-sentient robotic lifeforms, generally about five centimetres tall. Like the Transformers, Scraplets are capable of transforming between two modes: they transform from various humanoid or animal modes to nuts or bolts.

Marvel Comics
In the comic, the Scraplets first appeared as an interplanetary cloud which a Decepticon cargo freighter passed through on its voyage from Cybertron to Earth. During the incident, the pilot of the freighter was infected by the Scraplets and involuntarily brought them to Earth along with him.

Scraplets feed on other robotic lifeforms, which makes them very dangerous to them. Scraplets generally travel in large packs in search for robots, and upon finding one, they eagerly jump onto it, fastening themselves on the robot's armour plating. Once fastened, the Scraplets release some kind of corrosive agent that both allows them to sink partly underneath the armour plating and make them impossible to remove. Using the raw materials of the host, a single Scraplet can multiply itself many times over, creating further Scraplets and rapidly overwhelming the host.

As the feeding continues, the host robot begins to rust and decay, withering away until its inevitable death. Scraplets are - in effect - very contagious, so other robots in the vicinity of an infected robot risk infection themselves.

Scraplets also have the ability to combine large numbers of themselves into a single, giant, humanoid-shaped creature, in order for them to attack large-scale threats/food.

However, Scraplets have one major weakness: plain old water is fatally poisonous to them. When doused with water, a Scraplet loosens its grip on the host robot and falls away, allowing it to be safely destroyed without harming the host. Furthermore, they have no taste for organic material, which means that humans can approach them without fear.

The origin and homeworld of the Scraplets has never been explained in the comic.

Dreamwave Productions
In the Dreamwave comic series, "Scraplet" was also derogatory term for small Micromaster Transformer used by larger Transformers.

IDW Publishing
Among Prowl's suggestions for ways to execute a captive Megatron was "a single Scraplet taken orally".

Transformers: Timelines
Scraplets appeared in the "Shattered Glass" storyline by Fun Publications. These scraplets came from a mirror-universe, and actually repaired robots, instead of destroying them. However, they do eat dead Transformers such as their Cliffjumper.

Fun Publications
Scraplets appeared in the "Dungeons & Dinobots". They were a potion designed to heal damaged Transformers. They feasted on dead metal, leaving healthy metal untouched. The metal is either recycled into living metal or more scraplets. They're fatal to Zombies. They were usually contained in vials, as the air in Cybertron's Shatterverse is loaded with water vapor, which kills them.

Transformers: Prime
Scraplets appeared in the Transformers: Prime Like their comic book counterparts, the Scraplets ignore organic material. Unlike their comic book counterparts, they do not transform, and are spherical in shape. They are capable of flight, and their mouths contain rows of razor-sharp teeth, which make a sound like a chainsaw when they are about to attack. While Scraplets will eat anything metal, they prefer living metal the most, making them a threat to Autobots and Decepticons alike, however like their comic incarnation their harmless towards organics, making vulnerable to attack by humans. The Scraplets demonstrate a weakness to cold temperatures. They are regarded as the most dangerous vermin on Cybertron. The episode "Scrapheap" marks their first appearance outside the comics.

Animated series
In "Scrapheap", the Scraplets were recovered from a crashed escape pod buried in the Arctic. Once thawed, they invade the Autobot's HQ while Optimus and Arcee patrol the Arctic leaving Bumblebee, Bulkhead, Ratchet, Jack, Miko, and Raf to repel the enemy. The Autobots' human allies helped to fight against them. The Scraplets were frozen when Bulkhead lured them through the Ground Bridge back into the Arctic.

They are among the few lifeforms let remaining on Cybertron. In "Orion Pax" Pt. 3, Jack Darby tries to stop a horde Scraplets from eating Vector Sigma. When an Insecticon catches up to him, Jack uses the Scraplets as a weapon to destroy the Insecticon.