The nice thing about the Healing Factor is it's capable of bringing characters back whole From a Single Cell, even with exactly their previous hairstyle! It's usually really cool to watch too, as entire limbs grow back in gorgeous CGI (or not). Usually this is helped along with liberal use of Shapeshifter Baggage to avoid that pesky "conservation of mass" physics insists is accurate. However, sometimes physics teams up with Horror and Squick and puts its foot down on these shenanigans... or rather, puts its foot 'on'.
A character who has Appendage Assimilation can regenerate from just about any wound but with one caveat: he has to attach a working limb to that stump or consume an equal amount of bio-mass for the Healing Factor to work. So you'll have this character get torn and rent to pieces, then pull themselves together and keep fighting (and/or bantering) as if nothing had happened. Usually they never die to blood loss (which makes sense, as presumably the same power on a smaller scale works to keep their blood in their veins), and any lost limbs (head included) will still function and be reattachable, if not autonomous and capable of fighting.
The root of this power varies, it may be because as The Virus, they can "assimilate" any and all organic matter into themselves regardless of compatibility (so he might improvise by attaching snakes to his arm stump). Or they might have powerful Nanomachines that can do just about anything provided enough biomass. Magical or demonic powers of some kind are also popular.
As has been mentioned ad nauseam (pun intended), this power is not pretty to look at. Disturbingly, this can be taken even further though by having foreign limbs assimilate imperfectly. The skin won't match, the "seams" will look like burn wounds, mismatched limbs sizes are common and if the character had to make do with two left feet, well he can write off any dance competitions for a long while.The result of all this reattaching will be they look like a gooey Frankenstein's Monster, though some have enough healing factor that they can make new limbs look like they're natural... err, that is to say, natural to their body. Others might decide to forgo using human limbs and graft whatever is 'handy', eventually resulting in a Shapeshifter Mashup.
To really freak out viewers and their enemies, they might be picky about whose limb(s) they use, or even use another character's face this way. Expect them to do a bit of Showing Off the New Body just to rub it in. Compare Partial Transformation and Cannibalism Superpower.
- The manga Blade of the Immortal has Manji, the immortal owner of the titular blade. There's a whole story arc devoted to this trope, including a mad scientist that's trying to copy Manji's immortality onto other people by switching his limbs with others. Frequent occurances of Body Horror and Theyd Cut You Up ensue.
- Happens fairly frequently in Claymore. As a matter of fact, this is the only reliable Healing Factor that "Attack-type" Claymores have. They can regenerate complete limbs, but it takes months and the new limb will be vastly weaker than the original one, so if a severed limb is destroyed, they've lost it permanently. "Defense-type" Claymores, however, have the full Healing Factor and can completely regenerate limbs in very short order with no loss of limb strength.
- Aptom in Guyver.
- In Naruto, Juugo saves Sasuke's life by using his shapeshifting ability to turn a large chunk of his body mass into an improvised skin graft. In the next battle he gets injured himself and heals his injury by stabbing an already fallen soldier with a stinger and absorbing his flesh.
- In Ninja Scroll the series, one of the villains repaired herself through improvised surgery, going as far as using animal body parts.
- In X 1999 the TV series, Fuuma heals his grievous injury (he got his arm and half his face blown off) by assimilating the lat of his Quirky Miniboss Squad
- In Neon Genesis Evangelion, Unit 01 does it against the 14th angel, ripping it open and swallowing it's S2 engine to use for itself. She also rips off the angel's right arm to make herself a new left one.
- In Busou Renkin after Victor wakes up and we find that Kazuki has the same power, to show how DBX-esque their powers are, they rip each other's arms off and put them on themselves. However, when they do the arms change to match their bodies (the beefy arm shrinks and becomes paler, while the smaller arm grows and tans.
- Sesshomaru of Inuyasha, after losing his arm, could steal the arms of other demons and attach them to the stump. Problem was, he's a ridiculously powerful demon, and every arm he used became useless in the span of a day or two. Naraku offered him a human arm containing a shard of the Shikon jewel, which was sufficiently powerful for Sesshomaru to use, with the added benefit that it allowed him to wield Inuyasha's anti-demon sword. Eventually, the arm burst into flames. He later tried using a dragon's arm, but gave up on the practice after a related near-death experience.
- One of the Pillar Men from JoJo's Bizarre Adventure did this by taking an arm off a corpse to replace one that was severed in a fight, then remarked about how the arm "didn't fit right".
- Takahashi's Mermaid Saga
- One of the creepier moments is seeing someone graft someone else's arm or leg onto her own body.
- Probably the creepiest is the woman who switches her face through this trope. It's completely voluntary too - she cuts off one face without anaesthetic to disguise herself with the new face - then later switches them back again.
- In Franken Fran there is a great deal of mix-and-match surgery going on; so much so that it practically drives the plot.
- The short story version of Trinity Blood once had Abel regenerate a severed arm, by using the mouth on his other hand to eat it.
- Zodd the Immortal of Berserk reattaches a severed arm, pausing only to bash an enemy across the room with it.
- From Marvel Comics, the Terror assimilates all sorts of body parts. It's a necessity, since his body and any biomass he assimilates into it rapidly rot. In the "League of Losers" storyline, he even gets Arana's arm after she dies.
- The priest in the Uwe Boll take on House of the Dead.
- The monster in Jeepers Creepers.
- In Strings, set in a world of marionettes, the wealthy take replacements for their damaged limbs from slaves. As long as the titular strings are still connected to the limb it functions normally. The main villain has had his whole body, except for his head and one arm, replaced.
- In the last novel of Alastair Reynolds' Revelation Space trilogy, we learn about the Scuttlers, a long-dead intelligent species of insect-like creatures who had this ability—and used it as part of their culture. A socially-successful Scuttler had a unique set of appendages from trading them with others. Scientists who believe it was a natural ability (rather than the result of genetic manipulation) theorize that the Scuttlers evolved in the equivalent of a crowded lobster tank—an environment so hostile that it was advantageous not just to be able to drop limbs, but to reattach them if for some reason they don't get eaten by the predator you were escaping from.
- The Igors in Discworld do this for a living. At least one Igor in Ankh-Morpork has taken up veterinary surgery, meaning that a stolen horse whose markings are too distinctive for resale may reappear on the market with a different set of legs.
- A humorous variation takes place in the space opera parody Bill the Galactic Hero by Harry Harrison: As the sole survivor of a space battle the titular hero was reassembled using the random bits left lying around, which leaves him with two right hands, amongst other things.
- In The Dresden Files the "super-ghouls" appear to flow back together no matter how badly they've been damaged. In Changes Susan severs the Red King's hand (with a holy sword no less), and the thing still crawls back up his leg and reattaches itself to his arm.
- When Nick O'Donohoe's Wyr go from human to wolf or vice versa, parts (such as fingers and tails) fall off. The Wyr then eat their own shed appendages to conserve biomass.
- Kai from Lexx does this often—getting decapitated or bisected is his routine.
- Star Trek: Voyager have the Vidiians, a race that suffers 'the phage', an inccurable degenerative disease. They survive by stealing bodyparts from other alien races and replacing their failing organs and other tissues. Their medical sciences are far in advance of federation standards as a natural result.
- The Neo Organism from Kamen Rider ZO does this with metal from its surroundings.
- This is how regeneration is described in 3rd edition Dungeons and Dragons.
- A Dark Sun adventure from Dungeon 56 featured the last troll on Athas, who'd salvaged the severed limbs and heads of his necromantically-slain fellows and grafted them onto himself. The issue's cover art resembles a troll version of a Vedic deity.
- The Heroes of Horror supplement contains a monster called a cadaver golem, the result of an accident in the creation of a flesh golem. It is highly intelligent (golems are usually mindless) and has the ability to swap out any of its body parts for those of other creatures, even its brain (which it can use to gain the learned skills of the victim).
- Orks in the fluff of Warhammer 40,000 can assimilate any orkish body part as long as they have some means of attaching it (duct tape, staples, welding apparatus, etc). They can even regenerate from having their head cut off and sewed/stitched/stapled/welded/taped back on... And it doesn't even have to be their own body the head is reattached to.
- In Legacy of Kain: Soul Reaver, Melchiah has to do this constantly: He was raised with the smallest part of Kain's vampiric gift, and so retained much of his human weakness, including his constantly rotting body, which he has had to remedy by flaying and grafting human flesh onto himself, becoming a giant monster made of human bodies in the process.
- This is how you heal your player character in Prototype - by absorbing people whole.
- At the very end Mercer is blown up by a nuke. A crow tries to eat a random piece of flesh... which begins eating the crow. This apparently is enough for Alex to start rebuilding himself.
- In the prologue of Shadow Hearts, Yuri gets his arm torn off. He then calmly reattaches it. This is the only time in the entire game where he displays any kind of Healing Factor. A popular theory states that this is the game compensating for its player characters fighting all sorts of nightmarish creatures; all of the characters you meet have this ability, but they can only do it a number of times equal to their hit points.
- Unity in Skin Horse is a stitched-together zombie creature who is capable of reattaching her limbs if they become detached, and also of doing the same trick with limbs that are not hers: there's a fight scene where one of her hands is mauled by a werewolf, so she replaces it from one of the corpses lying about. One of the werewolf corpses.
- In Exiern the immortal mage cuts off a random civilian's hand to replace his own, complete with a bad pun.
- Jigsaw from the superhero webcomic Zodiac is an interesting example, as he doesn't depend on this trope for survival. He grafts various body parts onto his body because he wants to.
- The Makuta does this- absorbing Nidhiki, Krekka and Nihvawk in order to become a giant Shapeshifter Mashup One-Winged Angel form in Bionicle:Legends of Metru Nui.
- Men in Black has Alpha AKA Agent A. K's former mentor who got greedy with alien technology and now uses it to integrate alien body parts into his body
- In The Simpsons Treehouse of Horror XIV has Frink's father turn into this after being resurrected. Hilarity Ensues.
- Some species of nudibranch can assimilate the intact stinging cells (nematocysts) of the siphonophores they eat. The stinging cells remain fully functional.
- As plants lack any immune system, grafting parts of different plants (even of different species) to one another is standard horticultural practice. Ornamental roses or cacti are commonly assembled this way, with hardy rootstock attached to a more-fragile upper stalk. Certain fruits such as avocados are propagated entirely from high-quality branches grafted onto less-marketable, but healthier, trees.