i once had a dog who had a pet rock..... she would bring it with her everywhere, take it outside her doghouse for about 5 minutes each day, dip it in the water bowl every few hours, and even take it to the top of her slide and drop it down the slide. then one day i heard her barking like crazy so i went outside to see what was up. she was in her doghouse barking at her rock and smacking it back and forth with her paws until she finally threw it out and never played with it again.
TL;DR? my dog had a pet rock and eventually had a domestic dispute and beat the rock mercilessly before abandoning it.