Creature — Bird Wizard 3/1, 3U (4)
Common
Flash (You may cast this spell any time you could cast an instant.)
Flying
When Crookclaw Transmuter enters the battlefield, switch target creature's power and toughness until end of turn.
Illus. Ron Spencer

10/1/2009: When figuring a creature's power and toughness, apply effects in a series of sublayers in the following order: (a) effects from characteristic-defining abilities; (b) effects that set power and/or toughness to a specific number or value; (c) effects that modify power and/or toughness but don't set power and/or toughness to a specific number or value; (d) changes from counters; (e) effects that switch a creature's power and toughness. This means that 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.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern