The Clown is an uncommon Hardmodeenemy that only appears during Blood Moons. The clown's primary weapons are smiley bombs which will do extreme damage to a player or NPC when they explode, but will not destroy tiles. Touching the clown itself inflicts melee damage, and has a chance to inflict the Confused debuff.
Once you have defeated at least one Clown in a world, the Clothier will start selling the Clown costume.
Notes
Most Clown spawns are overriden by common enemies during Blood Moons on the Mobile version.
Although Clowns are a relatively rare enemy, at least one Clown will usually appear over the course of any Blood Moon during Hardmode (more if the player is in the Jungle or has an enemy spawn increasing item in effect, like the Water Candle and/or Battle Potion).
Although the Bananarang rare drop is a weapon, due to its stackable nature (a feature shared only with Light Discs), the Clown may drop multiple Bananarangs at a time (up to four at most).
As Clowns are the only Hardmode exclusive Blood Moon enemy, it makes them the only enemy that has a consistent chance of dropping the KO Cannon.