Icicle

Icicles are frozen water drops that have sometimes appeared in the Mario series.

Appearances
They first appeared in Phase 16 (17 in Japan) of Mario Bros. as obstacles that attacked by dropping from under the top platforms and pipes, where they constantly regenerate. They would also kill the player if they touched an icicle while it was still attached to the ceiling. Touching it while it is still a liquid droplet or using the POW Block will prevent the icicle from being formed, though this will not award any points. However, the POW Block will also cause fully formed icicles to drop prematurely.

In Super Mario Bros. Special, icicles could be defeated by fireballs. They do not regenerate.

In Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3, throwing an egg at them would cause them to fall down from the ceiling.

Wario has met icicles as well in Wario Land: Shake It!, in the level Slipshod Slopes. They appear in a cove part, and seem to be gigantic. When executing the Earthshake Punch, these big icicles will fall down, and crush any enemy underneath (defeating 5 enemies with those icicles is also a mission in that level). When Wario hits a falling icicle, he'll get hurt. Wario can also stand on those icicles as if they are platforms. However, the fallen icicles will break after a short time. when broken, new icicles will grow on the piece of ceiling the old ones were fallen off. There are giant icicles as well in Freezing Fields.

Icicles reappeared in Super Princess Peach in the Gleam Glacier world and behaved the same way as they did in Mario Bros..

They also make a minor reappearance in Super Smash Bros. Brawl. When fighting on the Ice Climbers' stage, the Summit, they act the exact same way they did in the original Mario Bros., except they are invincible and cannot be melted this time.

They are found in World 3-3 and 3-Castle of New Super Mario Bros. Wii, along with giant falling icicles that Mario can walk on. Icicles come in different sizes, and when the smaller icicles fall, another one forms a few seconds. Mario and company will take damage if they come in contact with one.

Icicles appear in Luigi Bros., an additional game featured in Super Mario 3D World. Like the other enemies in Luigi Bros., Icicles behave in the same way as Mario Bros., which this game is based on.

Giant Icicles reappear as stage hazards on the Mushroom Kingdom U stage in Super Smash Bros. for Wii U with their appearance from the New Super Mario Bros. series. They occasionally fall from the top of the screen and can damage fighters. They appear in all four variations of the stage.

A similar obstacle is the Falling Spike in Super Mario World; however, Falling Spikes attack due to proximity as opposed to maturity.