Pot of Gold Coins
From the Super Mario Wiki
The Pot of Gold Coins is, as its name implies, a pot of gold coins that belongs to Murphy the leprechaun. It was featured prominently in The Super Mario Bros. Super Show! episode "Mighty McMario and the Pot of Gold".
Unlike ordinary coins, the coins in this pot are magical and grant Murphy with good luck as long as they are in a safe place. Should the gold coins get lost or stolen, Murphy's good luck will instead turn bad until the pot is retrieved.
In "Mighty McMario and the Pot of Gold", King O'Koopa had stolen the Pot of Gold Coins from Murphy, turning the poor leprechaun into a jinx. On top of that, Murphy's bad luck triggered a rain storm that slowly started to flood his home of the Shamrock Kingdom.
Mario and his friends attempted to take back the coins from King O'Koopa, but Murphy's interference triggered enough bad luck to get them all caught. Eventually, Mario found a way to use Murphy's bad luck against King O'Koopa, and they succeeded in defeating him. Murphy then got his Pot of Gold Coins back, which in turn brought back his good luck and ended the rain. Murphy's reunited luck even caused Mario to literally drop in on lunch.