Elf

Elves (sometimes elfs) exist in many continua, most notably in modern fantasy or fantasy-influenced settings, but have their origins in regional folklore. Many 'contemporary' elven varieties are based (sometimes loosely, sometimes not) on the elves of The Lord of the Rings. LotR also popularized the plural spelling elves over the more traditional elfs.

The presence of elves often assumes the presence of humans, because they are a deviation from the local 'human' model yet are very close in general form. Elves generally have the same body structure as humans, but are usually finer-boned and slim rather than bulky. Their height varies, but is nearly always shorter than humans (save in some continua where they are referred to as 'tall and fair') ranging from the slightly shorter elves of Dungeons & Dragons to the tiny elves present in many fairy tales. Their features are usually more delicate than those of humans, and they usually cannot grow facial hair. One of their identifying features is the shape of their ears: long and thin or short and leaf-shaped, they are always 'pointy' in some way.

(Note that having pointy ears alone is not an identifying factor for being a local elf variety. Vulcans from Star Trek and Hylians from The Legend of Zelda are both pointy-eared species that are not elves. Calling them elves is incorrect and bad.)

Culturally, elves are often characterized as wise, passive, magical, close to nature, and culturally static. In many settings, elves live much longer lives than humans (or are immortal), and their ways change very little because it may take centuries for even one generation to pass. It was an unfortunate stereotype that elves as a concept were designed to be holier-than-thou or simply better at everything than humans, leading to a common characterization of elves being short-sighted or haughty. Many modern inclusions of elves seek to deviate from this model, such as the elves of Dragon Age, which retain little of their ancient dignity; the house elves of Harry Potter, which are tiny, unattractive creatures who work for wizarding families; or the elfs of Discworld, which are more closely modeled on the elves of ancient myth: self-centered, unpleasant, rather dumb but extremely cunning, and afraid of iron.

Sometimes there are multiple variations of elf in a canon, whether it is simple cultural difference or a 'racial' difference that implies that they are as different from each other as elves and dwarves are.

In speaking of dwarves, many elf varieties have either a contrast or an outright rivalry with the local dwarves. It's easy to see why they might fight like cats and dogs: Dwarves are subterranean, elves are usually forest-dwelling. Dwarves like rocks, elves like trees. Dwarves are often bearded, stumpy, and token-masculine as a culture. Elves are not usually bearded, are willowy, and usually are somewhat androgynous... etc.

Half-elf, half-human individuals exist in many continua that contain elves, and are perhaps the most common humanoid hybrids in fantasy (despite often being rare in their own continua).

Elves tend to speak languages with many dipthongs and accents throughout many continua. (See Grelvish.)

Elves and the PPC
Mary Sues love elves. Elves live for a long time, and are nearly always described as more beautiful and graceful than humans... sometimes preternaturally so. Elves usually are portrayed as able combatants that focus on speed and evasion rather than brute strength... perfect for a Mary Sue that doesn't want to hide her gorgeous figure behind bulky armor. Elves are often very magical, which attracts Sues and their desire to be special and have power. On the whole, elves commonly have an element of tragedy to them, or at least a bittersweet side to their often-long lives... which also attracts Sues and their tragic backgrounds.

There are several agents that are elves. Elven Mary Sues probably do not amuse them.