Spark Fairy

Often in fiction, fairy creatures, fireflies or other magical insects get depicted as simple little points of light rather than going for a full design for something so tiny we'll never get a good look at it.

The obvious inspiration is fireflies. It's funny how fireflies often end up behaving in usual and rather magical ways. In a way, it's an example of the connection between light and magic.

Do not confuse with By the Lights of Their Eyes; this trope is about Energy Beings or Faceless Masses that may or may not sparkle. See also Ghost Lights.

Examples of Spark Fairy include:

Anime and Manga

Used in Inuyasha the Movie: Fire on the Mystic Island for the spirits of the dead.

Film

In the 1999 film version of "A Midsummer Night's Dream," the fairy characters have this form at the beginning of the movie, when they arrive, and at the end, when they leave.
The ghosts/angels in the opening of It's a Wonderful Life are seen as celestial bodies that flicker when they speak.
Done with the tail-end UFO in Close Encounters of the Third Kind.
Bit from Tron is the personification of an on-off bit. It is basically a Disney sidekick fairy in Cyberspace.

Literature

Some of the smaller spren in The Stormlight Archive are described as this such as lifespren (small green sparks) and rotspren (tiny red points of light).

Live-Action TV

Merlin has this regard to the Sidhe. They are depicted as blue points of light, but due to Merlin's magic powers, we get some lovely FX shots of them in all their scary magical glory.
This trope actually becomes motive for murder in Furuhata Ninzaburou — a very eccentric editor decides to change the lime-green points of light to red points of light for the hell of it. The original artist flipped out and bashed the editor's head in. (Art is Serious Business.)
Doctor Who has the nanogenes in "The Doctor Dances".
- The Megara from "The Stones of Blood".
On Star Trek: The Next Generation, the microscopic crystalline aliens referred to humans as "ugly bags of mostly water."
In the Buffy the Vampire Slayer episode "Fear, itself", Willow summons a fairy like this to guide her out of the haunted house. However, the spell is warped by the demon haunting the place.

Theatre

This used to be how Tinkerbell in Peter Pan was always depicted, based on the theatrical practice of using a small light reflected from a mirror and a tinkling bell, until Disney came up with its marvelous design for the film.
- It still is in pantomimes.

Video Games

In The Legend of Zelda: Ocarina of Time, Navi is depicted as a ball of glowing light with dragonfly wings sticking out.
- The same is used for fairies in Majora's Mask and Phantom Hourglass.
  - The Healing Fairies in The Legend of Zelda: Twilight Princess are also the same way.
The fairies in the first Quest for Glory game are little balls of light of various colors. The ones in the fourth game, however, are far more detailed.
All the Animal Crossing games have fireflies shown as points of light, until you catch one of them.
A magical spell in Nox summons a small swarm of fairies that circle Jack until an enemy approaches, at which point they go kamikaze on the enemy. The fairies never appear as anything more than yellow sparks.
Fairies in Stonekeep can apparently switch between spark-fairy mode and detailed mode.
Flying points of light (presumably insects) are an important plot element in one Are of Uru. They're attracted to your character, but dislike crossing water or getting rained on.

Western Animation

The Princess and the Frog: The scenes with Ray's family have both detailed fireflies and points of light....maybe fireflies that are farther away?
The Pyreflies in Disney's Atlantis: The Lost Empire were depicted this way, more or less.