Let's face it, some characters are pretty damn hot. Other characters may have raging hot passion. But in this trope's case, we find fictional creatures that are literally Hot-Blooded (or anything that's close enough to blood).
This type of being usually has an implication (or at least a possibility) of a temperature difference that's caused by metabolism-based weirdness. This makes some sense, as there are several organisms in Real Life that have an average body temperature that's higher than the human average.
Characters that can play with fire tend to exhibit this trope, along with many fire-related monsters like dragons, salamanders, and fire-related familiars. Lava beasts, fire elementals, and other creatures that actually made of some heat related substance are another trope altogether.
- Shishio, the season 1 big bad of Rurouni Kenshin. He was shot in the head and lit on fire before being left for dead. The fire left him disfigured, and all of his sweat glands were destroyed. As such, he has incredibly high body temperature, which (apparently) grants him almost superhuman speed and strength. The downside is that he can only fight for about fifteen minutes before the heat buildup kills him.
- JoJo's Bizarre Adventure:
- The Pillar Men have each mastered a type of fighting style called "Mode", where they freely transfigure their own bodies to emulate Elemental Powers. Esidisi's Mode is Heat Control, which entails heating his blood to 500 degrees Celsius then extending his blood vessels from his body and injecting his blood into an opponent. The results are just as horrifying as they should be.
- A lesser example would be Robert E.O. Speedwagon during Phantom Blood. It's never really explained how or why, but Speedwagon is so hot-blooded that he could melt Zeppeli's frozen arm just by holding it to his chest for a minute. Unfortunately, his hot blood makes him unable to use Hamon Techniques.
- In Kill la Kill, Ryuko is normally simply Hot-Blooded, but when she finally confronts her father's murderer her rage reaches a boiling point. That is to say, her blood is literally seen to boil, driving Senketsu into a frenzy.
- The Titans of Attack on Titan have extremely high body temperatures, which appears to increase along with their size. The Colossal Titan radiates superheated steam thanks to its lack of skin, and another Titan, twice the size of the Colossal, is so hot that it causes nearby vegetation to combust.
- In PS238, Suzi has an internal body temperature which can melt lead, which appears to stem from her radioactive nature. Incidents where she loses her temper are explained as "gas leaks".
- Supergirl's blood was burning-hot during her Red Lantern tenure in Red Daughter of Krypton. This is true of Red Lanterns in general, as the Red Rings' energy replaces their blood. As such, the removal of a Red Ring from their host would, under the majority of circumstances, result in their death.
- Runaways has a variation; while it is unknown if Karolina's Majesdanian blood is especially hot, it is supercharged with solar energy, a fact that the vampire Topher learns the hard way when he tries to feed on her.
- Wonder Woman (1987): Medusa's blood steams, and the pool of blood from her decapitation gets hotter rather than cooler until Pegasus is reborn from it.
- In Pokémon Reset Bloodlines James notes that Red has an unusually high body temperature when they shake hands.
- In Earthsong9405's Infected AU, Twilight Sparkle was bitten years ago but didn't turn infected. The bite did, however, raise her body temperature and metabolism.
- Downplayed in The Touch Of Green Fire. Shego's plasma powers cause her to have a body temperature that's two degrees above the average. She also has a higher blood pressure than normal.
- Inverted in Love Worth Waiting For. Elsa was born with a very low body temperature. When she was an infant, her parents feared that she was ill because she was so pale and cold to the touch.
- What happens when you piss off someone upgraded with Extremis in Iron Man 3. (Volcanic Ghost Chili level)
- The Assblasters from Tremors. As their name indicate, they fart fire to fly in a rocket-like manner.
- Inversion: it's implied in Frozen that Elsa's body temperature is colder than the average person's.
- Werewolves in Twilight. (Perhaps that's why they so rarely wear shirts.)
- The Marat in Codex Alera are slightly warmer than humans. This is important in the first book, when one is trying to sneak into a forest guarded by creatures who see in infrared.
- Sauron himself in The Lord of the Rings. The reason why his ring was glowing on his hand was because he was inhumanly hot.
- Invoked in The Sookie Stackhouse Mysteries (books that were the basis for True Blood); werewolves and other shifters are mentioned several times time as "running hotter" than their human counterparts.
- The "vampires" of I Am Legend are humans with a disease that (among other things) sends the body into overdrive. They run a fever of about 103 Fahrenheit as a baseline.
- Dragons of A Song of Ice and Fire do this. In fact, wound them and leave the weapon behind, and it may start to glow with the heat depending on how high quality the iron or steel is. Bronze and copper are likely to fare worse and could well start to turn molten if left too long (and goodness knows if they can give the poor dragon blood poisoning or not). Good luck trying to play vet, though.
- Simes in Sime Gen have a body temperature noticeably higher then that of Gens and children. This incidentally means they don't get sick as often as many germs can't tolerate the higher temperature.
- In a novel based on Magic: The Gathering, a Black-aligned vampire is set to fight a Red-aligned Geomancer in arena-style combat. The vampire manages to evade the torrents of stone and dirt, sink his fangs into the mage's neck and begins draining him dry... At which point the Geomancer turns his own blood into lava. Cue burning vampire.
- Anyone in Eden Green whose needle symbiote takes over their body completely begins to exhibit elevated body temperature, immediately noticeable to non-infected people.
- In The Inheritance Cycle, dragon blood is described as being roughly the same temperature and consistency as boiling tar.
- True Blood has its Werewolves.
Alcide: We run hot.
- In Farscape, Scarrans are extremely hot, and can project this heat as a weapon. Compare with Sebacceans, who are colder than humans and vulnerable to hot temperatures. Scorpius, being a hybrid of both races, needs cooling rods implanted in his head to survive.
- In the Supernatural Season 4 finale, Sam Winchester was said to have reached body temperature of 150F (65C) when he was killing Lilith, courtesy of the demon blood he was using.
- Marcos Diaz/Eclipse on The Gifted. His blood glows and when enough of it was spilled in a car the car exploded. A member of the Morlocks has similar blood and another mutant's blood melted through solid objects (although that may have been acid blood instead).
- Foreigner's "Hot-Blooded", with the singer saying he's got "a fever of 103."
- Dungeons & Dragons: Remorhaz - hot enough that nonmagical metal weapons melt on contact and if it swallows you it's game over, instant death, no save, do not pass go, do not collect £200.
- Pathfinder has Xotani, a gigantic worm whose title is The Firebleeder. Dealing too much damage to it in one attack (read: an amount large enough to actually harm it) triggers the equivalent of a flamethrower as burning blood sprays from the wound.
- Warhammer 40,000 has the Avatar of Khaine, which has molten iron running through it's veins. It's also Wreathed in Flames.
- Psionics: The Next Stage in Human Evolution features a somewhat realistic example of how this would play out in real life. The pyrokinetic ability Temper, Temper, Temperature can be used to raise the body temperature of living things. Raise it enough and they'll die from boiling in their own skin.
- Many Fire-typed Pokémon are described as having a flame-producing sac or other such organs in their bodies. Some Pokémon like Magcargo and Heatran literally have magma for blood.
- The Ax-Crazy bioweapon Alexia Ashford from Resident Evil Code: Veronica's main method of attack is slinging her blood at her foes, which combusts on contact with the air. Another host of T-Veronica, Manuela Hidalgo shows these same powers, though she's not nearly as evil as Alexia. It can be assumed that the fire-based attacks of her father Javier's V-Complex form run on the same principal as well, as they spring from Veronica too.
- The various Mutons in Xcom Enemy Unknown and Xcom 2 are noted to have bodies that remain warm hours after their deaths. Dr.Tygan mentions this makes them quite disconcerting to dissect.
- Monster Hunter: Dire Miralis is so superheated that its body boils oceans and decimates their ecosystem.