Rulings

• 2011-09-22
  "You" refers to the controller of Curiosity, which may be different from the controller of the enchanted creature. "An opponent" refers to an opponent of Curiosity's controller.
• 2007-02-01
  Drawing a card is optional.
• 2007-02-01
  If put on your opponent's creature, you do not draw a card when that creature damages you. The creature has to damage your opponent in order to have this work.
• 2007-02-01
  You draw one card each time the enchanted creature damages the opponent. This is not one card per point of damage.
• 2011-09-22
  Curiosity doesn't trigger if the enchanted creature deals damage to a planeswalker controlled by an opponent.
• 2011-09-22
  Any damage dealt by the enchanted creature to an opponent will cause Curiosity to trigger, not just combat damage.