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 Land. If a Fire Snake saw Mario, it would chase him by bouncing and try to touch him with it's flaming body. A Fire Snake could only be defeated by either hitting it with a Shell, 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. He could also make them to fall off an edge, however, they reappear after a few seconds.

Super Mario World
They later made rare appearances in Super Mario World only making an appearance in Outrageous. These are not proper snakes in effect that they are only faceless heads of fire that 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 game's 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.

New Super Mario Bros. Wii
They also appear in the game New Super Mario Bros. Wii with 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 them down on the course where they would spin out the racers if one was touched.

Mario Kart Wii
The same thing happens in Mario Kart Wii on two courses; one of which is Desert Hills itself. They also appeared in Grumble Volcano where near the end they hopped out of pipes on the side of the course. They have a new appearance in this game; they are a larger fireball in front with eyes.

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.
 * In the SNES version of Super Mario Bros. 3, the Fire Snake has eyes, which it never has in the original NES version.
 * Fire Snakes were originally written into the desert sequence of Super Mario Bros. The Movie but were cut for unknown reasons, possibly due to budget. However, concept artwork does exist.