Lucky and Cookie are a romantic pairing in the show. They both work at Shelter 17 and help find homes for puppies.
"Rebound" shows the first time that Cookie likes Lucky as more than a friend. In this episode, Rebound knocked Lucky and Cookie trying to find Niblet. The two of them seem smitten being piled up on each other, before Cookie yelled at him to get off her belly.
In "The General", Cookie was getting fed up with the boy dogs because they treat her like "one of the guys". Later when Dolly (The General) arrived Cookie became more upset that all the boys were falling for her, but she got especially upset when Lucky started to fall for Dolly. Seeing that Cookie was upset, Dolly had a private talk with Cookie. During the talk Dolly then realized that Cookie wasn't upset about all the guys, but mostly about Lucky. Cookie then admitted to Dolly that she has a crush on him.
In "Lucky the Dunce", when Lucky is preparing the plan to get the six puppies adopted, Cookie says "I love the way he does that," Squirt replies (with a mirror in his mouth) "Yeah, its as if you can see the gears working in his head." Cookie replied (sort of sweating) "Yeah, that's what I meant."
In "Lucky Has to Move" Cookie shared a farewell nuzzle with Lucky, thinking he was leaving Shelter 17 forever. She later cried when she thought she was hearing his voice.
In "The General", not much is shown that Lucky likes Cookie but at the end of the episode when Cookie gets her bow, Lucky looked happy and said to one of the dogs "That's Miss Cookie to you" then went back to admiring her new look.
In "Rebel Without a Collar" it's shown that Lucky returns the crush that Cookie has on him. When a coyote named Fang (who was mistaken for a dog) was brought to the pound, Cookie started to like him, which made Lucky really jealous. He then got really upset when Cookie left with Fang and almost admitted to Strudel that he has a crush on her.
In "Olaf in Love" a puppy named Kiki arrives at the pound with the ability to accurately predict things. She called Lucky and Cookie out as being more than just friends, to which Lucky nervously told her she wasn't right and quickly changed the subject to finding her a human.
In "When Niblet Met Giblet" Niblet falls in love at first sight with a dog named Giblet. A lot of romantic tentions between Lucky and Cookie arise. When Niblet sets off to be reunited with Giblet, Lucky decides to follow him and Cookie insists she comes along too, to which Lucky reluctantly agrees. During their journey, Cookie was saved by Lucky after she was swept away in a fast flowing water current. In his state of panic, he remarks, "Do you have any idea how much you mean to me?" She answers no and questions how much she really does mean to him and he responds, "Plenty." Later, after catching up with Niblet, Lucky gets a new perspective and realizes that he shouldn't always just focus on work, but rather value the other dogs' feelings. Lucky attempts to show his true feelings to Cookie, in which he even puts his paw on hers, but then gets suddenly interupted by Niblet. At the end, Niblet decides he can't be with Giblet anymore due to his job as a Pound Puppy and says "Love and duty don't mix. Just ask Lucky and Cookie." He then explains that it's obvious they love each other, but can't be romantic because it would be uncomfortable for the team.
In "Lucky Has to Move" Lucky, thinking he's about to leave Shelter 17 forever, shares a farewell nuzzle with Cookie.