The Saint Patrick (Event) is an event that went live on March 11, 2016. In a fashion similar to the Easter Egg Hunt events, the player must collect as much as possible, which sometimes appear when an enemy is killed, in order to progress through the event. You also have a chance to collect a lucky Pot of Gold that is worth 20 as well (40 if you bought the Double Gold Booster!).
Normally, a player adds only 1 to his meter for every one picked. However, the update introduced two new bundles which both contain a head item that multiplies the collected either by 2x or 4x. The Lucky Beret multiplies it by 2x while the Leprechaun's Hat multiplies it by 4x!