Princess Eclair

Princess Éclair was the damsel-in-distress that Luigi rescued from the clutches of the monstrous Chestnut King. However, as it turns out, Princess Éclair was actually the king's lover, who had been turned into a monster by the sinster Crepe. This complicated story is told by Luigi when Mario talks to him throughout the events of Paper Mario: The Thousand-Year Door.

During Luigi's adventure, the green-clad plumber fell in love with Princess Éclair. However, after he discovered that the Chestnut King was Princess Éclair's fiancée, Luigi lost the hope of ever forming a romantic relationship with the princess.

She is also mentioned in Luigi's five-book series "Super Luigi", which is sold in Paper Mario: The Thousand-Year Door.

Trivia

 * An Éclair is actually a pastry in real life.