Dragon Coin

From SMWiki

A Dragon Coin ( ) is a special coin with a Yoshi face on it. Despite the fact that an Info Box in Super Mario World referred to them as Dragon Coins, they are commonly known as Yoshi Coins. Found in most Super Mario World levels, each is worth one coin and collecting five will give Mario a 1-Up. Any additional Dragon Coin will give Mario a subsequent 1-Up, and once five more are collected they'll disappear from the level. They are not used in castles nor most ghost houses from the original game.

In the GBA remake Super Mario Advance 2, the collection of all five Dragon Coins is recorded on a status screen. Collecting every dragon coin in the game will result in a special movie where dozens of dragon coins fall from the sky and stack up. After which a Peach Coin bearing the princess' image replaces the dragon coins and can be recollected indefinitely.

Hacking glitches

Avoid placing Dragon Coins on a sub-screen boundary, otherwise half of the coin will not disappear, and if the coin is collected from above, the player can get 99 extra lives for about 5 seconds, because it gives you unlimited amount of Dragon Coins. Also, don't place too many coins in one level. This is frowned upon because it lets the player get more extra lives.

To avoid the former, hit F2 in Lunar Magic. This will actually show you the subscreen boundaries.