Rulings

• 2013-04-15
  Switching a creature's power and toughness twice (or any even number of times) effectively returns the creature to the power and toughness it had before any switches.
• 2013-04-15
  Effects that switch power and toughness apply after all other effects that change power and/or toughness, regardless of which effect was created first.
• 2008-10-01
  Effects that switch power and toughness are always applied last when determining a creature's power and toughness, even if other power/toughness-changing effects are created later in the turn. For example, if you activate Phantasmal Fiend's first ability, it will become 2/4. Then if you activate its second ability, it will become 4/2. Then if you activate its first ability again, it will become 3/3.
• 2005-11-01
  Note that the wording "Effects that alter the creature's power alter its toughness instead, and vice versa, this turn" has been removed.