I was led to believe that chocolate is very bad for cats anyway. I'm not sure what attracts them to it, but our cats show a lot of interest when my wife is having chocolate.

Ah, [link|http://www.petpeoplesplace.com/Advice/cats/feeding/02.htm|here's the link]:

and a quote:

"Even in relatively small amounts chocolate is poison to cats and dogs. Chocolate contains caffeine and theobromine, two different types of stimulants that affect the central nervous system and the heart muscle, as well as increasing the frequency of urination."

The author does point out that there are chocolate drops made especially for pets.