|Yellow and Red Coins|
A Blue Coin is a coin that is a blue-colored variant of the Yellow Coin. When Mario interacts with its hitbox, the coin counter is incremented by 5 instantly, which appears over time in the coin count because it only updates every other frame. Mario's integral HP is also increased by 5 gradually. The coin loads some Coin Twinkles and then unloads.
These coins can spawn in one of three ways.
- Certain enemies spawn Blue Coins upon death, like Medium Piranha Plants such as those in Whomp's Fortress, Mr. I's, and Beach or Shellless Koopas. Blue Coins are also spawned by Ground Pounding a Big Goomba, but not by killing it any other way, and by killing the head of a Pokey. Oddly, upon breaking a Crazy Box or throwing a Chuckya, five Yellow Coins are spawned rather than a Blue Coin, even though both would increment the coin counter by the same amount.
- When Ground Pounding a Blue Coin Block, a set number of Blue Coins will appear for a limited amount of time. If collected before the timer runs out, the coins and block will be unloaded. Before the block is Ground Pounded, the blue coins are loaded, but invisible and intangible.
- When sliding down the Cool, Cool Mountain slide, including during the Big Penguin Race mission; sliding down the Princess's Secret Slide, which also has a Blue Coin Block; and sliding down the Tall, Tall Mountain slide. These blue coins act differently from other blue coins. They slide down the slide similarly to how Mario does, and bounce a little.
Blue Coin Clones
Although it has been possible to clone Blue Coins since the basics of cloning and handsfree holding were discovered, it was thought impossible to clone them productively; that is, to collect more coins than normally possible by cloning them. However, it was discovered that by quickly getting to a loading zone, which is only possible in Wet-Dry World, the coin could be both cloned and recollected. Originally, it was thought that the only way to reach the loading zone in time was to use an Overflow Jump, which required visiting Parallel Universes to do. However, it was later found that it can be done using only a moderate amount of speed via a negative-height jump.