The 3-Up Moon is a bonus in Super Mario World. As the name suggests, it gives Mario three 1-Ups. Unlike the 1-Up Mushroom, this is an object, not a sprite. Also unlike the 1-Up Mushroom, a 3-Up Moon won't reappear when Mario reenters the level, even from the overworld. Sometimes, beginner hackers (Moonymoonymoons is a great example to one such a beginner hacker) tend to create bonus rooms with a ridiculous number of 3-Up Moons; this has become a source of parody, and is one of the things that you should never do in a serious hack.
The 3-Up Moon is also the icon of Lunar Magic.
Locations Of 3-Up Moons
- Yoshi's Island 1
- Donut Plains 4
- Vanilla Dome 3
- Cheese Bridge Area
- Valley of Bowser 1
- Forest Ghost House (Exit Level 1E6)
- Chocolate Island 1 (You need to enter the first warp pipe to make the moon appear in this level)
The 3-Up Moon is Extended Object 18 and Direct Map16 Access Tile 6E.
You should avoid inserting the Moon through Direct Map16 Access, because it allows the 3-Up Moon to reappear. The code that prevents it from appearing again is only used by the Object that spawns this Map16 tile, NOT the tile itself, which can only run code when something is touching it. Also, it is also advised that you use the Moon very scarcely, about once per world at most, as too many per world may result in too many lives. For that same reason, it's also advised that you place Moons in hard-to-find and/or hard-to-reach places. If you have trouble doing this, consider just not using the Moon at all, as there are other ways to give people extra lives, such as 1-Up mushrooms.
The aforementioned code to prevent the 3-Up moon from reappearing again makes use of the 12-byte large RAM table at $7E:1FEE. As soon as a 3-Up moon is collected, a bit is set for that level to indicate it has been collected in that level. It uses $7E:13BF, the starting level number, to index this.