Super Crown

The Super Crown is a power-up item that made its debut in New Super Mario Bros. U Deluxe. It is a puffy, mushroom-like pink headgear surrounded by a golden chaplet with eyes.

New Super Mario Bros. U Deluxe
The Super Crown can only be used by Toadette; other characters only get a 10-coin bonus. If Toadette picks one up in a level, she transforms into Peachette, a Princess Peach lookalike that gives her the ability to Double Jump and perform Peach's Floating Jump, controlling identically to the Flying Squirrel form (without the wall-clinging ability). Additionally, she automatically gets boosted out of pits, lava, or poison; however, if Peachette attempts the maneuver twice in a row, she will fall into the hazard and lose a life. The Super Crown's top appears to resemble the mushroom head of Toadette, being pink with white spots.

Captain Toad: Treasure Tracker
The Super Crown reappears in Captain Toad: Treasure Tracker for the Nintendo Switch in version 1.2.0. The Super Crown appears in the Special Episode after Chaos in the Grand Labyrinth is beaten, and is the final treasure required to complete the entire episode.

Mario Kart Tour
The Super Crown reappears as Peachette's emblem and an icon for the Peachette Cup in Mario Kart Tour.

New Super Mario Bros. U Deluxe

 * North American website bio: "When Toadette finds one of these, she can transform into the super-powered Peachette. (Sorry Luigi-only Toadette can use this item!)"
 * European website bio: "An exclusive power-up when playing as Toadette. By collecting this, Toadette becomes Peachette, allowing her to double-jump, float slowly during freefall, and get a boost back up if she falls into a pit!"

Trivia

 * The concept of the Super Crown transforming Toadette into another character and granting her their abilities is similar to that of the caps in Super Mario 64 DS.