I got curious and checked what the differences between the two were, and found this picture that explains perhaps the simplest way to tell them apart: the crocodile has a more pointed snout, while an alligator has a broader one.
A side note, the choice of letters may "muddy the waters" somewhat: at first glance, one might connect the capital A with an alligator (even though it's used to depict a crocodile), and C with a crocodile!