Super Acorn is a power-up. Mario or another playable character can use it by touching it.
If Mario or another playable character in New Super Mario Bros. U uses it they will turn into a flying squirrel. It only appears in New Super Mario Bros. U. In flying squirrel form, a player can glide short distances.
They are first seen when the playable characters in New Super Mario Bros. U are launched by the Airship's hand into The Great Tree and send the Super Acorns flying all over the Mushroom World. Then the heroes hit the tree flying squirrel enemies, called Waddlewings, fly out of the tree and join Bowser, increasing his army. Bowser's minions stuff the Super Acorns into ? Blocks. If a player hits a ? Block, a bad guy stuffed a Super Acorn in it will pop out and can be obtained.