I would advise that you make the ears slightly thicker than I made mine (one of them broke off-- but I fixed it with hot glue. You can't even tell now, can you? XD)
First, take straight up yellow clay and make a flat round shape. Then cut out a rounded triangle for the "bite".
Sorry I forgot to take a pic before I added the details! But It's not too complicated anyway, right?
Use a ball point pen with retractable ink to make the circle details. Just make sure you don't press too hard, otherwise you might get an inky cracker =(
Use an x-acto knife to detail the edges, and then use your thumb to smooth out the harsh lines just a bit.
The mouse is made by mixing 2 parts white to 1 part yellow clay. Here's all the body parts I used, labeled (click for a bigger picture). The assembly is pretty self-explanatory.
Use a toothpick to poke a hole in the cracker for a jump ring (if you're making it into a pendant), and add little indentations for eyes.