Adjustable Polymorph

Transmutation (Polymorph)
Level: Alchemist* 4, Artificer * 4, Bard * 4, Magus * 4, Shaman * 4, Sorcerer */Wizard * 4, Summoner * 4, Warlock * 4
Components: V, S, M (a small piece of doppelganger flesh)
Casting Time: 1 Standard Action
Range: personal
Target: you
Duration: 1 minute/level (D)
Saving Throw: -
Spell Resistance: -
  When you cast this spell, you can assume the form of any Small or Medium creature of the Humanoid type. If the form you assume has any of the following abilities, you gain the listed ability: Darkvision 60 feet, Low-Light Vision, Scent, and Swim 30 feet.
  Small creature: If the form you take is that of a Small humanoid, you gain a +2 Size Modifier to your Dexterity.
  Medium creature: If the form you take is that of a Medium humanoid, you gain a +2 Size Modifier to your Strength.
  as a Swift Action you can alter the disguise (within the limitations above). For example, you could transform yourself into a halfling, then a lizardfolk, then an elf, and so on. You can change your form a number of times equal to your Caster Level.