Petco: Free Bag of Purina Pro Plan Dog or Cat Food by Dana Zeliff on January 31, 20142014-01-31in Coupons, Pet Deals Disclosure: This post may contain an affiliate link. WOW!! Petco is offering up a coupon valid for a FREE Bag of Purina Pro Plan Dog or Cat Food! You must be a member of Petco Pals to redeem the coupon. Thanks, Freebie Shark!