Fire Snake

Fire Snakes are long, snake-like Podoboos with bodies made up of many fireballs. They have appeared as uncommon enemies in several Mario games.

Super Mario Bros. 3
The first appearance of Fire Snakes was in Super Mario Bros. 3, where they appeared in Desert Hill. If a Fire Snake saw Mario, it would chase him by bouncing and try to touch him with its flaming body. A Fire Snake could only be defeated by either hitting it with a Shell or Hammer, by having Mario touch it while he is empowered by a Starman or by having Mario whack it with his tail as either Raccoon Mario or Tanooki Mario or a stomp from Statue Mario. He could also make them to fall off an edge, however, they reappear after a few seconds. In the remakes of this game, Fire Snakes had eyes, while they never had them in the original NES version.

Super Mario World
While Fire Snakes did not make any appearances in Super Mario World, a similar enemy appeared in the level Outrageous. These unnamed enemies are not proper snakes but are only faceless heads of fire that attack just like Fire Snakes as they jump towards the player while leaving harmful remnant flames after each hop that last for a few seconds. Yoshi can eat them and the cape can destroy them. Mario can also safely bounce on them with the Spin Jump.

New Super Mario Bros.
Fire Snakes also appear as uncommon enemies in New Super Mario Bros. in the stage 2-5. These Fire Snakes will try to attack Mario by chasing him by bouncing and by trying to touch him, like in Super Mario Bros. 3. The Fire Snakes of New Super Mario Bros. can be defeated by throwing a Shell at them and by touching them when Mario is empowered by a Starman. He could also make them to fall off an edge, however, they reappear after a few seconds. They only appear twice. They have eyes in this game, similar to in the remakes of Super Mario Bros. 3.

New Super Mario Bros. Wii
They also appear in the game New Super Mario Bros. Wii acting like they did in New Super Mario Bros., but they have a new ability. After one or two hops, their heads will enlarge, then go back to normal size. They only appear in World 2-3.

Yoshi's Safari
In Yoshi's Safari, only two Fire Snakes appear as mini-bosses; in order to defeat these Fire Snakes, who will try to touch Mario and Yoshi, Mario must blast them repeatedly with his Super Scope.

Mario Kart DS
In the Mario Kart DS course Desert Hills, an Angry Sun shot Fire Snakes (they did not have eyes in this game) down on the course where they would cause any racers that touched them to spin out.

Mario Kart Wii
Fire Snakes also appear in Mario Kart Wii, acting the same way as they did in Mario Kart DS. They appear on two courses; one of which is Desert Hills from Mario Kart DS itself. They also appeared in Grumble Volcano where they are found near the end hopping out of pipes on the side of the course, attempting to spin out any racers that touched one. They have a new appearance in this game; they have eyes on their heads.

The Adventures of Super Mario Bros. 3
Fire Snakes made a few minor appearances in The Adventures of Super Mario Bros. 3.

Princess Toadstool for President
In "Princess Toadstool for President", Mario and Luigi end up in Dark Land and while there they get ambushed by many enemies, including a Fire Snake.

Crimes R Us
In "Crimes R Us", the Koopalings brake in to the Mushroom Kingdom Treasury, using a Chain Chomp to open the barred window, a Ptooie to blast a hole in the wall, and a Fire Snake to bust a hole in the roof.

Trivia

 * The Fire Snakes of Yoshi's Safari are blue, possibly symbolizing their status as mini-bosses, as a blue flame is hotter than a red one. Additionally, the Fire Snakes of Yoshi's Safari have eyes on all their body segments, instead of just one.
 * Fire Snakes were originally written into the desert sequence of the Super Mario Bros. film, but were cut for unknown reasons. Scripts state that they "[...]resemble moray eels, their mouths filled with pointed piranha-like teeth," and that "They gnaw through the skin, burrow into the body cavities, and lay their larvae. It can take weeks for the host to die."