Princess Lipid

Princess Lipid is a white figure in Mario & Luigi: Bowser's Inside Story that saves Luigi from falling deep into mucus. Once Luigi is out of the mucus, she gives Mario and Luigi badges.

Trivia

 * Though Princess Lipid has the term princess in front of her name, she is never revealed to be royalty.
 * Due to her Japanese name, she may be made out of mucus.