Curiosity

• WWizards of the Coast2011-09-22
  Official Ruling
  "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.
• WWizards of the Coast2011-09-22
  Official Ruling
  Any damage dealt by the enchanted creature to an opponent will cause Curiosity to trigger, not just combat damage.
• WWizards of the Coast2023-09-01
  Official Ruling
  Curiosity doesn't trigger if the enchanted creature deals damage to a planeswalker or to a battle.
• WWizards of the Coast2023-09-01
  Official Ruling
  You draw one card each time the enchanted creature deals damage to an opponent, no matter how much damage it deals.
• WWizards of the Coast2023-09-01
  Official Ruling
  If you control Curiosity and it's enchanting an opponent's creature, you won't draw a card when that creature deals damage to you. The creature has to deal damage to one of your opponents for the ability to trigger.

Rulings via Scryfall