Red Coin

Red Coins are coins that sometimes appear along with Yellow Coins in the Mario series. The differences between a yellow coin and a red coin differ by game, but usually, red coins serve as important items to collect to get a reward.

Super Mario 64
Red Coins appeared in Super Mario 64, and returned in its remake, Super Mario 64 DS. Each Red Coin is worth two Yellow Coins. Collecting all 8 Red Coins in one level makes a Power Star appear over a Star Marker. In Super Mario 64 DS, Some Bob-omb Buddies have the ability to detect red coins when the player talks to them.

Super Mario Bros. Deluxe
Red Coins are once again seen in Super Mario Bros. Deluxe. In the game's Challenge Mode, they (along with Yoshi Eggs) can be collected to obtain medals. Each stage contains 5 Red Coins, and collecting them all will earn the player that stage's Red Coin Medal if they successfully reach the end.

Super Mario Sunshine
Red Coins make another appearance in Super Mario Sunshine. Similar to Super Mario 64, collecting all eight in a level would make a Shine Sprite appear. However, Red Coins do not affect the player's total amount of Gold Coins and are treated as a completely different currency altogether.

Red Coin Secret Levels
In addition, red switches are located at the starting platform of Secret Levels, and when the player Ground Pounds the red switches, eight Red Coins appear and the timer is activated. Mario must then collect all 8 Red Coins before time runs out or he loses a life and must restart the level.

New Super Mario Bros.
In New Super Mario Bros., there are Red Rings in several levels, and if Mario or Luigi walks, jumps or swims through one, eight Red Coins appear. If he collects them all in the time limit, he is rewarded with a power-up. If Mario or Luigi are already using a power-up worth more than a Mushroom (i.e. a Fire Flower), he gets a 1-Up Mushroom instead of a power-up.

New Super Mario Bros. Wii
Red Coins and Red Rings also make a return in New Super Mario Bros. Wii. They serve the exact same function as in the preceding game and they will still give the player a power up if all coins are collected. However, small Mario collecting the coins would make a Fire Flower (or other power-ups of a similar power) instead of a Mushroom. Like before, if the player had already gotten a Fire Flower or similar power-up, they would get a 1-Up Mushroom after collecting all the Red Coins.

Super Mario 3D Land
Red Coins later appear with Red Rings in Super Mario 3D Land. Here, Mario must go through the red ring, then collect the red coins that appear before they disappear, like in other Mario side-scrolling games. Unlike other games, however, Mario must now only collect 5 of these coins.

New Super Mario Bros. 2
Red Coins appear once again in New Super Mario Bros. 2. Like in the previous New Super Mario Bros. games, Mario/Luigi must collect eight of them to earn a power-up, a 1-Up Mushroom, or a Golden Mushroom (only in Coin Rush mode), depending on his current form. When Mario/Luigi touches a Red Ring, Red Coins could appear in predetermined locations, or fall from the sky in parachutes.

New Super Mario Bros. U
Red Coins, along with Red Rings, will reappear in the upcoming Wii U title and newest addition to the New Super Mario Bros. series, New Super Mario Bros. U. Once again, all eight of them must be collected for an item to appear.

Super Mario World 2: Yoshi's Island
Red Coins are first seen in Super Mario World 2: Yoshi's Island, in which they are hidden behind regular Gold Coins. Red coins have a slightly red tint to them, so they just barely stick out as different amongst gold coins. When alone, neither feature is dramatic enough to be unambiguous. The only way to tell for sure which Gold Coins hide Red Coins is to grab them or use a Magnifying lens. Though visually the same size as gold coins, red coins are actually slightly larger, so that they are easier to grab. There are 20 Red Coins in each level, and grabbing one adds one point to Yoshi's score tally at the end of the level.

Yoshi's Island DS
In the sequel to Yoshi's Island, Yoshi's Island DS, Red Coins work the same way as they did in their first appearance; however, the Magnifying Lens was absent in that game. If the player can collect all the red coins in the level, the player gets a better score upon completing the level.

Mario Party-e
In Mario Party-e, Red Coins serve as one of the main collectibles in the minigame Waluigi's Reign. They are worth more than Yellow Coins, giving the players five points when obtained.

Mario Party DS
In Mario Party DS, Red Coins replace Coin Bags in bonus mini-games unlike the previous versions of the Mario Party games. They are, like Coin Bags, worth five Coins. They are obtained like Coin Bags too; rarer and sometimes harder to acquire.

Mario Hoops 3-on-3
Red Coins appear in Mario Hoops 3-on-3 under the name 10 Coins. They can be found in ? Panels, and as evident by their name are worth ten normal Coins. They are only found if the player manages to combo the dribbling of acquiring the coins without being interrupted.

Trivia

 * In Super Mario Sunshine, the symbol on the Red Coin slightly resembles Barry.
 * In Super Mario 64 and Super Mario 64 DS, red coins are worth the same as 2 coins, but in New Super Mario Bros. and New Super Mario Bros. Wii, they are worth the same as one coin.
 * Super Mario World has flying Red Coins that are worth five regular coins if collected, but they're unused.
 * Red Coins are the possible precessors to Purple Coins from the Super Mario Galaxy games, as Mario needs to collect a certain number of each to get a Power Star.