Magma Cube

Magma Cubes are hostile mobs with dark red and black skin and red, orange and yellow eyes found around The Nether. When killed, they release 2-4 smaller versions of themselves in addition to Experience Orbs, similar to Slimes. When they move, they jump up and momentarily unravel into several layers, giving them the appearance of a spring and revealing a molten lava core inside.

Appearance
Magma Cubes are reddish brown blocks with vaguely similar eyes to Creepers and Slimes, but bright orange. Although they look like normal slime size, when they jump they separate into 8 layers in a spring-like fashion, revealing a bright orange lava core. They release the same fire particles as spawners upon landing.

Drops
Big and small sized Magma Cubes have a 25% chance to drop a single Magma Cream, which is essential for Potions of Fire Resistance. Tiny Magma Cubes do not drop any magma cream.

Behavior
In their passive state, Magma Cubes move slowly, jumping forward every two seconds or so. Upon spotting a player, Magma Cubes will jump towards them more quickly, but the player can still outrun them. Also, they will try to damage the player by jumping directly on top of them. However, they cannot damage other mobs like this.

Combat
Fighting Magma Cubes can be very rewarding, as they can drop a large total amount of experience (12-28 for a large one, 4-6 for a small one), and Magma Cream is used to make Potions of Fire Resistance, which can be a life saver in the Nether and cave exploration. Magma Cubes are difficult to fight, however, especially the large ones, which have practical health due to their  armor points, and then split into 2-4 small Magma Cubes, which each split into 2-4 tiny Magma Cubes, thus giving a large Magma Cube an effective total health of  -  and each small one an effective total health of  -, and that is not including the fact that when they split, overkill damage is obviously not carried over. However, they don't do much damage (only for the large one), and they are rather slow (though they can jump very far). It is not suggested that you attempt to fight a large Magma Cube with only a sword, but a small one can be killed in 2(diamond) or 3(iron/stone) hits, and tiny Magma Cubes can be killed with one hit from any sword. If you hit the Magma Cube while it is jumping at you, you can interrupt its attack. It will take 5(diamond)/6(iron)/7(stone) hits to kill. Large Magma Cubes are more challenging, and a bow is suggested. Once it splits, back away (especially if it splits into 4) and attack the small Magma Cubes with arrows. The tiny Magma Cubes can be killed with one hit from a sword or an arrow charged to medium or full. The tiny Cubes appear to only be able to damage you with their bottom side, so if you can stay at a higher elevation than them, you can target the remaining small Cubes before dealing with the tiny ones.

Trivia

 * Magma Cubes cannot swim in lava, only jump along the bottom. Thus, they can get trapped in deep lava, although they will not drown. They seem to move very slowly in both water and lava.
 * Magma Cubes seem to be the Nether equivalent of Slimes. Although they appear similar, the components of their texture files are quite different.
 * Contrary to popular belief, Magma Cubes are actually less abundant in the Nether Fortresses than in the rest of the Nether due to fewer large flat surfaces to spawn on.
 * Every Magma Cube size drops experience orbs, not only the smallest cube. This means that killing a big cube and all its spawnlings would grant the player up to 28 experience, as opposed to 5 experience of other hostile mobs.
 * Magma Cubes only have a 25% chance of dropping Magma Cream, but these odds and the number of dropped items can be increased with the Looting Enchantment.
 * Despite trying, Magma Cubes are unable to jump in water, although they can move around. They will drown if completely submerged. They will however, split into smaller slimes and regain their air.
 * Unlike tiny slimes, tiny Magma Cubes can still hurt the player.
 * Unlike Slimes, which are rare and only appear below layer 40 in certain chunks of the normal world, Magma Cubes can appear anywhere in the Nether.
 * Magma cubes are often found in lava, since they are unaffected by it, a trait shared by all Nether mobs.
 * Like Slimes, when a magma cube is not chasing the player it will hop in one direction.
 * Magma cubes can be spawned in The Overworld if a Monster Spawner is modded to spawn them. They do not require Netherrack. As of Minecraft 1.1, the player can spawn them in Creative Mode without modding with a Magma Cube Spawn Egg.
 * It seems that Magma cubes (or at least tiny ones) can only damage you using their bottom side.
 * Magma Cubes seem to be immune to fall damage; A large has been witnessed to fall from a ledge that would normally be deadly, and yet take no damage. This also goes with Ocelots, Cats, Iron Golems, Snow Golems, and Chickens.
 * Armor potions give big/medium/small Magma Cubes 48%/24%/12% resistance against most attacks. It means that you need to deal at least /  /  physical damage to kill a cube.
 * Magma Cubes have much more time between jumps than slimes.
 * Magma Cubes appear to glow, as their eyes seem to stay bright at some low light levels.
 * Large Magma Cubes can jump 4 blocks high (over a wall)
 * Their texture file is called "lava.png". This is because of their lava core.

Bugs

 * They also seem to frequently glitch through walls, ceilings, and floors, to attack players on the other side; dropping down through the solid roof of a tunnel, for example, then glitching back up to the roof out of sword reach. Or they will lunge out through the walls of a tower while a player is descending via a gravel pillar, and push them off said pillar without causing attack damage.  They also seem to sink into Soul Sand, being invulnerable while merged inside a Soul Sand block, yet being able to jump up and attack from inside their protective glitch.
 * Like Slimes, right before they are killed, upon exiting to title screen and back to game, Magma Cubes will be alive again but flipped to the side and red as if they were about to die.