Here come the...

How they all begin...

All Pez Pals start looking like this, a generic head. This head will have holes where hats and beards and many other accessories can be added. Add some parts and pieces and they are transformed into different characters. Let's see how this works...
Head Holes

There are three different head hole designs on these characters. The first, from left, has a hole in the nose, cheek, one under his hair above his ear (not visible) and one for his hinge pin. The next one shown is the same except no hole in her nose (thank goodness) and the last and most recent issue has only a hole for the hinge pin.
Also...

Look for the Partial Cheek heads too (the one on the right is Hong Kong).

They can be as simple as Boys and Girls shown above.
Or...

Add one more piece and they can change. This is Boy with Cap. The hole in the hair can accommodate pieces just like the head holes.
Here are some more...

Shown above are Engineers, one on a red stem (3.9 Austria), one on a blue stem (3.8 USA) and one on a translucent blue stem (3.9 Austria). Also shown is Sailor.

Fireman (2.6 Austria and 3.9 Hong Kong), Sheriff and Policeman

It's the lifesaving duo. Doctor and Nurse. Nurse is on a DBP (818) stem.

Maharaja (2.6 Austria yellow, 2.6 Austria red, 3.4 Austria yellow), Pirate (3.4 no country marked green, DBP 818 no counrty marked blue) and Sheik.
Strange, you say?

This is a shot of the inner sleeve on the Pirate shown above. It's the same color as the stem.
And again I say strange...

Who might this be? I call him Albert Einstein. Was there really an Albert Pez? No. Kids were encouraged to interchange all the parts and pieces. Like a disguise. This was a Doctor Pez and somewhere along the way he lost his other pieces and gained a full head of hair.

Here's an assortment that shows some of the different turban colors for the Maharaja. And a cool grey stem guy. The grey stem is a 3.8 USA. Thank you, Jody!

Here's Mexican Boy. This is not a normal Mexican. Most will have a very large mustache/goatee. This one has what appears to be a normal Pez pal mustache. But, it's different than those too. Very strange.
And look at the new kids in town...

From left is Mariner, Shell, Alpine and Aral.
Give it a rest, Rob.