Frogs and Luck
Sometimes, cultures associated frogs with good and bad fortune.
In Japan, frogs are the symbols of Good Luck. One myth I read dealt with the idea that bullfrogs are descended from a great ancestor who could suck all the mosquitoes out of a whole room in a single breath!
Some myths are less favoring to frogs and toads. Some folklorists* have claimed that "If the first frog that you see in the spring is sitting on dry ground, it signifies that during the same year you will shed as many tears as the frog would require to swim away in." If, on the other hand, the first frog of spring jumps into the water, you'll experience misfortune all year! However, if the springs' first "hoptoad" come jumping in your direction, you will have many friends; if it jumps away from you, you will lose some. (sounds to me like it's best not to run into the first spring frog!)
Some less enlightened people associate frogs, and Toads in particular, as evil incarnations of demons or devils!