Spark

Sparks are orb-shaped creatures who continually emit pulses and flashes of electricity. They are mostly found crawling around walls and ceilings and moving across wires. Sparks are the first in a series of enemies in the Mario franchise that are balls of electricity, including Li'l Sparkies and Amps.

Donkey Kong Jr.
Sparks first appear in the Hideout Scene of Donkey Kong Jr. Red Sparks (also known as Globes ) continue to circle their own platform, but blue ones can travel to other platforms through static particles. These Sparks are generated by Mario in order to shock Donkey Kong Jr., preventing him from saving his father. Sparks are the rarest enemies in the game, only appearing in one stage (the Hideout Scene), while the other enemies all appear in two stages.

In the Coleco Adam port, the layout of the stage has been altered and there are no blue Sparks. Instead, they have been replaced by dangerous green water drops that come from the mouths of spigots and cracks in the ceiling.

Donkey Kong (Game Boy)
In Donkey Kong for Game Boy, only one Spark appears in Stage 6-4, rotating clockwise at a medium pace around a small platform in the path of a Conveyor Belt. It has the same behavior as the Sniper and Sukōpī seen earlier in the game, except losing a life from the Spark displays an electrocution animation. Unlike other appearances, the Spark in this game lacks eyes. This game also introduces a more common wire-crossing successor.

Super Mario Bros. 2
Sparks also appear in Super Mario Bros. 2 as uncommon enemies, usually encountered underground or in buildings. They circle platforms, though some can hover in the air if a Mushroom Block is pulled out from beneath them. Sparks can be defeated by throwing an object at them or using a POW Block near them. Sparks can't be jumped on and can hurt the player's character by simply touching them. In the NES version, Sparks have red outlines around their eyes; in the SNES version and other subsequent remakes, they have yellow outlines as well as an orange outer body outline. If the screen scrolls while they are in a specific position, they will automatically die.

Sparks changed slightly in Super Mario Advance. If the player is hit by one, they are knocked back and the screen flashes. In addition, an item called the Spark Chaser can be used to expel them from new jar interiors.

The Super Mario Bros. Super Show!
A Spark makes only one appearance on The Super Mario Bros. Super Show!, in the episode "On Her Majesty's Sewer Service". Having been dumped into the Tunnel of Doom, Mario and Luigi, while running from a Goomba, encounter a Spark that is quickly approaching. Mario and Luigi manage to avoid this Spark and the Goomba by creating a grappling hook out of a super spy hose nozzle and mini plunger; apparently unable to stop moving, the Spark and Goomba subsequently crash into one another, causing an explosion. In this appearance, the Spark featured does not appear to radiate any electricity.

Nintendo Comics System
Sparks are featured quite prominently in issues of Nintendo Comics System, appearing in such stories as "The Legend," "Bedtime for Drain-Head," and "A Mouser in the Houser." Like most enemies featured in the stories, they are shown to be intelligent and fully capable of speech.

Trivia

 * The name "Spark" is shared with a similar enemy from the Legend of Zelda series.