The Penguin Suit is a new suit that is in New Super Mario Bros. Wii. Hence its name it looks like a penguin. When Mario, Luigi, and the Toads put it on they gain two abilities. They can slide on their bellies like a penguin and destroy enemies with their beak and they can also, throw iceballs that can freeze an enemy similar to the Ice Flower. Mario and Luigi's overalls are a part of the outfit. The Penguin Suit lets the player swim more efficiently underwater, and even slide on ice and water without sinking, breaking any blocks they collide with.

Puzzle & Dragons: Super Mario Bros. Edition

These appear as one of the types of orbs.

Super Smash Bros. Trophy Descriptions

Super Smash Bros. for Wii U

Penguin Mario

"Ahh, the life of a penguin... So carefree. At last, Mario too can enjoy the feeling of gliding across the ice by donning the Penguin Suit. Not only that, but this suit unlocks other penguin abilities too! Mario can swim gracefully and, just like a penguin, dream of a day when he can fly."
Wii - New Super Mario Bros. Wii - 11/2009
Wii U - New Super Mario Bros. U - 11/2012