My mom's dog has a thing for really small potatoes. He won't eat or chew on them like other things, he instead carries them around and protects them like a loving mother. Then he buries them in the yard, digs them up a week later and brings the rotting potato into the house. We invariably throw it away, and he acts like we threw away his only son for about 4 days. It's sad, yet so weird.
I also gave the other dog a 9 volt battery, similar reaction to the lemon.