After completing the game for the first time and unlocking Superstar Road, the Propeller Hat and Penguin Suit power-ups from the first New Super Mario Bros. for Wii become made available from the Toad Houses located there. Once obtained, they can used in any level in the game.
Jump on the flagpole while the last two digits of your time are the same number. The number of fireworks that will appear depend on which number was the same. See the following fireworks by landing the last to digits tot he corresponding numbers: