PEZ have the following variations.

PEZ as a whole may come as totally silver or gold or any of a seemingly endless combinations of head vs. stem colors.  They may come in clear cases, thin cardboard boxes, in plastic bags, on cards, on platforms or in tubes.  PEZ dispensers may be the typical flip-back head type but also come as cars, trucks, mechanical-electrical toys, back pack accessories, and on and on.  PEZ may also license their name to companies that use the name but provide no dispenser at all.  An example of this is Johnny Lightning miniature cars.

1.  Heads:  May vary by hair color (Aral boy), facial expression(as in the case of TMNTs), eyes, position, size and so on.  They also may be soft such as in the PEZ Pets or squeezable as in the case of the monsters series.  Heads may be a solid color, translucent(crystals), have painted features or snap-on features.  The variety seems endless.

2.  Stems:  May vary by feet(thick or thin)(the platform upon which a PEZ stands) or no feet.  Their color is infinite and depends on the plastic mix used at the time of molding.  Stems may have names or shapes painted upon them as well as die cut shapes in them.  Stems may also be covered with "fur" as in the case of PEZ Pets.  Stems comes in several heights with the Japanese PEZ (minis) being much shorter than the standard PEZ stem.  Stems can be found also as cell phone straps, flashlights, ink pens, and so on.

Add the variations of PEZ heads and stems and the combination makes for a daunting task for any avid collector.  Top that with the decades in which PEZ have been made and the task grows in size again.  Add yet another wrinkle of country or origin and the collector will never be done!