Ghast

The Ghast is a floating jellyfish-esque mob that shoots fireballs from its mouth. Its body is a 4x4x4 block cube with several tentacle-like body parts emerging from the bottom. They first appeared in the Halloween Update.

Ghasts are able to spawn anywhere in The Nether, as long as there is sufficient space (5x5x5, occasionally 4x4x4; it is unknown whether this is a glitch or intentional). While an extremely rare occurrence, Ghasts may spawn near Portals in the regular world if given enough space to do so.

Ghasts normally float around with their eyes and mouth closed, making a sound like giggling children. They open their eyes and mouth when attacking. They scream when shooting or taking damage. The sounds that ghasts make are currently not affected by distance, so they always sound very close, regardless of their actual position.

Netherstone and imported Dirt blocks can be destroyed by the Ghast's fireballs. Netherstone will burn forever once struck, adding an extra hazard to fighting Ghasts. Stone Buttons can also be destroyed. Materials that cannot be destroyed include Cobblestone, Stone, diamond, Iron Doors, and Obsidian. If a ghast's fireball hits a portal (or close to it) the portal will be closed, requiring re-ignition, possibly by another fireball.

Ghasts will not fire at the player without line-of-sight, and they  cannot see through glass or portals, making safe scenic paths  through the Nether a viable possibility.

Fighting Ghasts
Ghasts attack with projectile fireballs. The player can reflect these fireballs by hitting them with anything before they impact, even bare hands or arrows. It is possible to kill Ghasts by reflecting their attacks back at them.

Ghasts may be hurt with normal weapons if the player can get close enough or has a Bow. Ghasts may also be set on fire, but will only be hurt for the duration of touching the fire/lava block it floats into. A similar effect is seen with Zombie Pigmen. Ghasts drop Gunpowder when killed, but this can be hard to collect - as it is the only mob that floats, the Gunpowder may fall into Lava or an inaccessible area.

Drops
Alpha:
 * 0-2 units of Gunpowder