Earn New Costumes
To earn a new costume for a particular area, beat Gladstone's time in all four stages to get a new costume from Donald. You meet Gladstone in the level that Huey, Dewey, or Louie were blocking.

Defeating Merlock:
After the Merlock splits in four, attack the one that has the shining diamond

Switch Costumes
If you have earned more than one costume, you can return to Gyro's Lab and in the corner on the far left is a machine that will let you choose a different costume to wear.

Special move:
Quickly collect five cogs to get one letter from the word "SPECIAL" in any level. Keep collecting cogs until the entire word is spelled out. Complete the level to learn a special move