Get Challenge Mode
Unearth the key item found on the 5th floor of the Summer stage's first dungeon to unlock the Challenge mode.
Unlock Shyacho character
Collect 10,000 pocos to save Hokotate Intergalactic Delivery, then choose to continue.
Easter Egg: Title Screen Fun
At the title screen where it says "press Start", press the X button to make a beetle appear. Once the insect is on the screen, you can use left and right on the C-Stick to turn it and forward to move. If you move the bug into the Pikmin that make up the logo, they will "interact" with the bug.
Press Y to make a Chappie appear. You can move it around the same way and press Z to make it eat Pikmin. To get rid of the creatures, press the L button. Press R to make the Pikmin run around the screen and then rearrange themselves to form the word "Nintendo."
Get Cinemas and Credits
Collect 10,000 pocos
Get Treasure Completion Movie
Collect all the pieces and rescue Looie.