Leprechaun o'Fyffe

Leprechaun o' Fyffe is a pet you summon by using the Pot o' Gold item. There is a chance that he will drop a coin when he jumps. He can drop any kind of coin but the lower value ones are more common. Like all pets, the leprechaun o'fiffe will walk next to you without going through blocks, however if you get to far away from him he will fly through blocks to you.

Tips
It is possible to farm his coins by making a room with a low ceiling, having o' Fyffe on one side of the door and you on the other. He will try to jump out (probably because he thinks it is simply an obstacle). If you place a block above his head he will jump even faster as he can fit through a 2 block gap.