Clown

The Clown is a rare enemy that sometimes appears during Blood Moons The smiley bomb it throws will destroy nearby blocks when it goes off, like a normal Bomb; this makes the Clowns a serious hazard to any structures. Ranged weapons are the most useful form of attack against clowns as they will explode when killed. You can use them to shoot the clown's bombs out of the air as well. Once you have defeated at least one Clown the Clothier will start selling the clown costume.

History
One way to defend your base against clowns is to line the walls with Dungeon Bricks, which are impervious to bombs.