Moneybag

Money Bags are purse-like enemies with about 20 coins in them.

New Super Mario bros.
In New Super Mario bros, you can see a Money Bag in level 5-2 in a secret tube. To kill it you approah the coin, and it turns into a Money Bag. Once a Money Bag chase it to the other tube. When there, you bounce on it 20 times. On the 21st time a 1-up mushroom appears.

Mini Games
It also appears in one of the puzzle mini games in New Super Mario bros.