I guess I shouldn't take all the credit for it...his mom fetches. When we went to pick Zeus up, that's all she wanted to do. So he probably learned from watching her. She fetched plastic straws, and we've used the same for Zeus. We've just kept reinforcing him - giving him treats when he does bring it back and giving him praise. And for the times he doesn't bring it back, I'll get it and bring it back for him. :D