The differences between alligators and crocodiles:
 

Alligators: 
The fourth tooth of an alligator’s lower jaw fits into a pocket on his upper jaw. 
An alligator’s snout is broader and more squared off.
 

Crocodiles:
The fourth tooth of a crocodile’s lower jaw fits into a groove in the side
 of his upper jaw—his tooth is visible even when his mouth is closed. 

How to tell alligators and crocodiles apart: the fourth tooth of an alligator’s lower
 jaw fits into a pocket on his upper jaw. The same tooth on a crocodile fits into a
 groove in the side of his upper jaw-his tooth is visible even when his mouth
 is closed. Also the alligator has a much broader snout than the crocodile.

Alligators are very large reptiles.  They are related to crocodiles.
Alligators and crocodiles look very much alike, but you can tell
 them apart.  Crocodiles have a fourth tooth that sticks out from
 the lower jaw on each side.  The alligator does not.  The alligators
 have flatter, broader heads.  Their snouts are rounded.
 An alligators snout is shorter than a crocodile's.

Alligators live in warm water.  They live in swamps, rivers,
 lakes, and other marshland.   They live in fresh water.
 Once in awhile they may go into the ocean for a short period of time.

Alligators are carnivorous.  They like to eat: fish, turtles, rats,
 snakes, mammals, and sometimes other alligators.
  They will eat almost anything they can overpower.

Alligators are found in warm areas.  They can be found in two places
 around the world, the southeastern United States and in the Yangtze
 River in China.  The Chinese alligator is the smaller of the two.  It rarely
 grows beyond 5 feet.  The American alligator is much bigger.  The
 average American alligator is usually between 6 and 12 feet long.

Alligators swim with most of their bodies under water.  The color of their
 skin usually blends in with the muddy, murky water.  The color of
 adult alligators dark, greenish dull brown.  Usually only their nostrils
 and eyes are above the water.  The young alligators
 are almost all black with yellow spots and stripes.

An alligator is a large reptile.  It has four very short legs.
  The tail of an alligator is very muscular and extremely strong.
  The tail helps it to be a strong swimmer.  A protective covering of
bony plates run down the back of the alligator.  They are under the skin.

The life span of an average alligator in the wild is about 30 - 35 years.
  Alligators in captivity can usually live up to 50 years.

Alligators are extremely flexible and quick.  Any alligator over the size
 of 12 feet long is very rare.  Alligators at one time were almost extinct. 

An alligator has about 80 teeth in its mouth at one time.
  When its teeth wear down its teeth are replaced by new teeth.
  An alligator can go through more than 2000 teeth in a lifetime.

Female alligators protect their nests.  They will lay between 30 - 70 eggs.
  She makes a nest of mud and different water plants on the side of a bank
 near a lake, river, pond, swamp, or marshland.  The eggs will hatch in about 60 days.

Alligators bellow, grunt, or croak.  Baby alligators peep when they hatch.
  The mother alligator carries the babies to the river in her mouth.
  In cold weather, the alligator digs a hole in mud and buries himself.
  He breathes slowly and sleeps until the weather warms up.

From the Really Rosie CD Carole King sings "Alligators All Around".

Do you need a way to thank your classroom volunteers?
  Give them a little alligator applause with this thank you
 poster.  To make one, cut a 3' x 3' square from blue bulletin
 board paper.  Use a permanent marker to write a message
 in the center of the paper. (for example, "Thanks for helping
 in our classroom! See you later, alligator!")  Next, invite each
 child to make a green handprint (fingers together and thumb out)
 on the edge of the poster; then write his or her name near the print.
  When the paint is dry have the child glue a wiggly eye and paper
 teeth onto the print.  Carefully, roll up the poster, tie a green
 ribbon around it and then present it to a special someone.

Alligator Ideas at Perpetual Preschool

Alligator Theme at First School

Alligator Crafts at DLTK

Alligator & Crocodile Activities at Everything Preschool

Five Little Monkeys & Alligator Flannel Board Patterns

Alligator Crafts at Enchanted Learning

Interesting Facts Gatorland

5 Little Monkeys Fingerplay Printables

Alligator Purse Flannel Board Printables

Pre-K Fun Theme Pages are for educational reference only! 
No copyright infringement is intended.
I do not claim any of these as my own ideas.  
They are shared from friends and fellow group members.  
Thanks for sharing all your great ideas!