Pink Coin

As of the 1.40 update, players were allowed to add s into courses.

A Pink Coin is a new type of coin introduced in Super Mario Maker. In SMM, shaking a regular coin will reveal a Pink Coin; in SMW2 they appear separately on the menu. Collecting five of these rewards the player a Key, which can be used to unlock a locked door. Up to ten Pink Coins can be placed in a course, five in the overworld and in the sub-level each. All Pink Coins are part of the same collection and all go towards one key, even if two sets of coins are put into each the main and sub-level.

Unlike the regular coins, pink coins cant be placed on tracks, inside any kind blocks or fall to the ground after the use of a POW block. They won't turn into bricks after using a P-switch either. However, players can make the task of collecting them less repetitive by forcing the player to collect them using shells, yoshi or by punching a block under them.

Checkpoint Behavior
Each time a player passes a checkpoint, the pink coins they currently have will be saved, meaning that if they die, they will continue with the same pink coins collected when they first met the checkpoint.

Re-activating a checkpoint (after activating the 2nd one) counts as a save.

If the player collects the last pink coin, obtains the key then uses a checkpoint, they won't keep that key after a death. Therefore, all the pink coin progress would be lost.

To remedy to that problem, it is advised to put checkpoints after the key doors so that the player saves their progress once they won't need the key anymore.

Trivia

 * Pink Coins strike a huge similarity in both appearance and functionality to the Red Coins, another type of collectible coins in the Mario series, and even share a similar sound effect when obtained as well.
 * They are identical in function to the Key Coins of Super Mario 3D World. In SMM2, Key Coins appear in the 3D World theme, but are referred to as Pink Coins.