New Super Mario Bros. U (WiiU)
Five bonus coins
If a multi-coin block is still active after you collect 10 coins from it, the final hit will release five coins.
Ground-pound or spin near a dancing flower and one coin will pop out. You can do this once per flower.
Grab a flagpole to stop the timer when the tens and ones digits match (and are not zero). The Super Mario Bros. course clear theme will play, fireworks will go off, and Toad will give you a power-up for your item inventory. The item you'll get depends on the number matched in the timer.
After clearing Peach's Castle, a "Save" option will replace "Quick Save" on the map screen menu.
Unlock Superstar Road
Clear Peach's Castle to open Superstar Road, the ninth world. In Superstar Road, each course is locked until you collect all the Star Coins in the corresponding world. For example, collecting all the Star Coins in Layer-Cake Desert (World 2) will open Superstar Road-2.
Unlock the Secret Island
Clearing Peach's Castle also opens the Secret Island. Inside the Secret Island's mushroom house you can view various records, such as number of coins collected, Goombas stomped, and goal poles reached.
Unlock Superstar Road-9
Superstar Road-9 will appear on the map screen after you've collected all the Star Coins in Superstar Road courses 1 through 8.
Here are the requirements to get stars to appear on your save file:
When you have all five stars, all the Toad Houses will reappear, and you'll be able to re-enter them as many times as you wish.