Rulings

• You can't cast Spark of Creativity without targeting a creature. If the creature becomes an illegal target for Spark of Creativity, none of its effects happen. You don't exile the top card of your library.2016-09-20
• If a card in exile has {X} in its mana cost, X is considered to be 0.2016-09-20
• If a land card is exiled this way, you can play that land card until end of turn if you have any available land plays.2016-09-20
• You must pay all costs to play the exiled card. You may pay alternative or additional costs. If the card has any mandatory additional costs, you must pay those.2016-09-20
• Spark of Creativity doesn't change when you can play the exiled card. For example, if you exile a creature card without flash, you can cast it only during your main phase when the stack is empty.2016-09-20