ShapeChanging changes from 3.5

References:

Please note that these are borrowed/based off of (in order to deal with server access issues) the copyrighted articles by Rich Burlew from; http://www.giantitp.com/articles/dC21fDHZ4tK8n5OjUm9.html and http://www.giantitp.com/Func0021.html (They may be changed to more accurately reflect the local rules.)

Arcane Casters:

The morph-related spells have changed. Some have been removed, some have been modified, and several have been added.

Alter Self: This spell is deleted and replaced by alter.
Animal Growth: This spell cannot target a creature that has had the Polymorphed template applied.
Animal Shapes: This spell is deleted and replaced by mass animorph.
Baleful Polymorph: This spell is deleted and replaced by turn to frog.
Enlarge Person: This spell cannot target a creature that has had the Polymorphed template applied.
Polymorph: This spell is deleted.
Polymorph Any Object: This spell is deleted and partially replaced by transmogrification. Other effects are deliberately removed as problematic, such as the ability to turn pebbles into humans.
Reduce Person: This spell cannot target a creature that has had the Polymorphed template applied.
Righteous Might: If the target of the spell has the Polymorphed template, they do not increase in size. They do not gain size bonuses to Strength or Constitution. If the creature already has been targeted by righteous might when it acquires the Polymorphed template, the size increase effect is suppressed for as long as the creature has the template. They still gain the damage reduction and natural armor enhancement effects.
Shapechange: This spell is deleted and replaced by infinimorph.

The Druid:

Replace the druid's existing wild shape, elemental wild shape, and thousand faces abilities with the following:

Wild Shape (Su): At 5th level, the druid gains the ability to change its shape into that of an animal once per day. The druid may apply the Polymorphed template to himself, as long as the assumed shape is that of an Animal of Small or Medium size. The effect lasts for 1 hour/druid level, or until he chooses to change back. Changing form is a standard action that does not provoke attacks of opportunity. Use the druid's class level for all effects related to caster level, rather than total Hit Dice; any other class that grants wild shape abilities stack with druid levels to determine caster level. This ability otherwise functions exactly like the Animorph spell.

The druid gains the ability to take the shape of a Large animal at 8th level, a Tiny animal at 11th level, a Huge animal at 15th level, and a Diminutive animal at 17th level. At 12th level, the druid can take the form of a Plant (such as a shambling mound) or a Vermin, with the same size restrictions as for Animals. At 19th level, the druid may take the form of an Animal or Vermin with the Swarm subtype. The druid gains additional uses of the wild shape ability at 6th, 7th, 10th, 14th, and 18th levels.

Elemental Shape (Su): At 16th level, the druid gains the ability to take the form of an elemental. Similar to wild shape, they may apply the Polymorphed template to himself, as long as the assumed shape is that of a Small, Medium, or Large elemental (air, earth, fire, or water). They may use this ability once per day, and the effects last 10 min./level or until he chooses to change back. This ability otherwise functions exactly like the wild shape ability. The druid gains additional uses of the elemental shape ability at 18th and 20th, and may take the form of Huge elementals at 20th level as well.

A Thousand Faces (Su): At 13th level, the druid may change his appearance at will as a standard action, as if casting the alter spell on himself. Unlike the spell, however, the druid may only use this ability while he does not possess the Polymorphed template.

Monster Changes:

The following are notes on how to alter monsters with natural polymorph abilities using the new rules. Technically, most of these notes could be figured out on one's own, but I thought it might be helpful to have them written down. This list only includes monsters in the SRD, but you can figure out the rules for other monsters based on these.

As a rule of thumb, if the creature can polymorph only itself and/or has a limited selection of assumed shapes, it gains the Shapechanging supernatural special ability, described below for a number of creatures. This allows it to use its Hit Dice as the caster level, and to maintain a shape indefinitely. Creatures with a large number of spell-like abilities that can polymorph other creatures as well simply replace that spell with a thematically appropriate selection of the replacement spells. Generally, I assumed that no creature should be able to naturally take the form of an Outsider, Elemental, Construct, or Undead without the use of spells. Finally, creatures capable of replicating specific individuals flawlessly get the Alter Shape ability, described below for the doppelanger.

   * Doppelganger: Replace the text of the Change Shape ability with the following:
       Alter Shape (Su): The doppelganger can alter its appearance at will as a standard action, as if casting the 
       alter spell on itself. Because the doppelganger does not carry equipment, it can duplicate the appearance of any worn  
       clothing or armor. The doppelganger can keep its appearance altered as long as it wishes, though it reverts to 
       its natural appearance when killed.
   * Demon (Marilith): The marilith can cast animorph, anthromorph, or xenomorph at will instead of polymorph.
   * Demon (Quasit): Replace the text of the Alternate Form ability with the following:
       Shapechanging (Su): A quasit can change shape as a standard action, applying the Polymorphed template at will. 
       The quasit only knows one possible assumed shape per Hit Dice (usually three). Each known assumed shape must be 
        a creature of the Animal, Fey, Humanoid, or Vermin type, and can be up to Medium size.
   * Demon (Succubus): Replace the ability to use polymorph as a spell-like ability with the following:
       Shapechanging (Su): A succubus can change shape as a standard action, applying the Polymorphed template at will. 
       The succubus can choose to assume the shape of any Fey or Humanoid of Small or Medium size and of the same gender, 
       and can maintain that shape until she chooses to apply a different Polymorphed template or end the effect.
   * Devil (Imp): Replace the text of the Alternate Form ability with the following:
       Shapechanging (Su): An imp can change shape as a standard action, applying the Polymorphed template at will. 
       The imp only knows one possible assumed shape per Hit Dice (usually three). Each known assumed shape must be 
       a creature of the Animal, Fey, Humanoid, or Vermin type, and can be up to Medium size.
   * Dragon (Bronze, Gold, and Silver): Replace the text of the Alternate Form ability with the following:
       Shapechanging (Su): A (bronze, gold, silver) dragon can change shape as a standard action, applying the Polymorphed 
       template up to three times per day. The dragon can choose to assume the shape of any Animal or Humanoid of Medium size 
       or smaller, and can maintain that shape until it chooses to apply a different Polymorphed template or end the effect.
   * Efreet: Replace the ability to use polymorph as a spell-like ability to use anthromorph as a spell-like ability once per day.      
       The efreet also gains the ability to use pyromorph three times per day.
   * Guardinal (Leonal): The leonal can cast animorph, anthromorph, or xenomorph at will instead of polymorph.
   * Lycanthropes: A lycanthrope uses its own rules for changing shape, and does not gain the Polymorphed template. 
       If a lycanthrope gains the Polymorphed template, however, it is always based off of the lycanthropes non-animal form, 
       even if the creature gains the template while in hybrid or animal form.
   * Night Hag: Replace the ability to cast polymorph at will as a spell-like ability targeting herself only with the following:
       Shapechanging (Su): A night hag can change shape as a standard action, applying the Polymorphed template to herself 
       at will. The hag can choose to assume the shape of any Animal, Fey, Giant, Humanoid, Magical Beast, 
       Monstrous Humanoid, or Vermin of Large size or smaller, and can maintain that shape until she chooses to apply a 
       different Polymorphed template or end the effect.
   * Ogre Mage: The ogre mage can cast animorph, anthromorph, or xenomorph at will instead of polymorph.
   * Phasm: Replace the text of the Alternate Form ability with the following:
       Shapechanging (Su): A phasm can change shape as a standard action, applying the Polymorphed template to itself at will. 
       The phasm can choose to assume the shape of any Aberration, Animal, Dragon, Fey, Giant, Humanoid, Ooze, Plant, 
       Magical Beast, Monstrous Humanoid, or Vermin of Large size or smaller, and can maintain that shape until it chooses to 
       apply a different Polymorphed template or end the effect.
   * Rakshasa: Replace the text of the Change Shape ability with the following:
       Alter Shape (Su): The rakshasa can alter its appearance at will as a standard action, as if casting the alter spell 
       on itself. The rakshasa can keep its appearance altered as long as it wishes, though it reverts to its natural 
       appearance when killed.
   * Pixie: Replace the ability to cast polymorph on itself once per day as a spell-like ability with the following:
       Shapechanging (Su): A pixie can change shape as a standard action, applying the Polymorphed template to itself 
       once per day.  The pixie can choose to assume the shape of any Animal, Humanoid, Magical Beast, or Vermin of Small 
       size or smaller, and can maintain that shape until it chooses to apply a different Polymorphed template 
       (on a subsequent day) or end the effect.
   * Titan: Replace the ability to cast polymorph on itself at will as a spell-like ability with the following:
       Shapechanging (Su): A titan can change shape as a standard action, applying the Polymorphed template to itself 
       once per day. The titan can choose to assume the shape of any Giant, Humanoid, or Monstrous Humanoid type of 
       Huge size or smaller, and can maintain that shape until it chooses to apply a different Polymorphed template or 
       end the effect.
   * Vampire: Replace the Alternate Form ability with the following:
       Shapechanging (Su): A vampire can change shape as a standard action, applying the Polymorphed template to itself at will. 
       The vampire can choose to assume the shape of a bat, dire bat, wolf, or dire wolf, and can maintain that shape 
       until it chooses to apply a different Polymorphed template or end the effect.