Kelly is a teenage Woolett girl and one of Star Butterfly and Pony Head's friends. She loves Goblin Dogs, and she is usually seen with her boyfriend Tad prior to their permanent breakup in "Lava Lake Beach". When first introduced, Kelly appears to be a creature made entirely of aquamarine hair, with her only other characteristics being eyes and legs. Near the end of "Goblin Dogs", however, she is revealed to be a teenage girl with brown skin, no apparent nose, and long bushy hair that usually covers her whole body and reaches down to her ankles. Underneath her hair, Kelly wears an oversized pink-and-white-striped sweater, black shorts, pink boots with aquamarine tassels that match her overgrown hair, and big round black-rimmed glasses. In "Starcrushed", "Lava Lake Beach", "Monster Bash", "Booth Buddies", and "Cleaved" Kelly wears her long hair tied in a ponytail with a pink hair tie. In "Lava Lake Beach" her long sleeves are folded up, and she wears purple sandals with socks. In "Stump Day", her winter attire consists of a purple sweater, a white scarf and purple pants and she wears her long hair tied in pigtails with a pink hair tie. In "Booth Buddies", Kelly wears a pair of white boots and a yellow dress with short sleeves, a white collar, and two buttons. In "Divide" and "Conquer", she wears a gray suit of armor with a matching helmet, a pink scarf, maroon trousers, and brown boots, while wearing her hair in a ponytail. In "Kelly's World", she wears a white T-shirt with a picture of a blue sad face and the words "Bummer Ville". Also, when her hair covers her entire body, her mouth is now visible at all times. In "Goblin Dogs", Kelly first appears as part of a long line of customers who want to buy Goblin Dogs, having saved a spot in line for Pony Head, Star Butterfly, and Marco Diaz. Whenever Marco tries to talk to Kelly, she remains silent. While waiting in line, the only sound she makes is the crunching sound of eating apples. Near the end of the episode, however, Kelly finally speaks up when Star, Marco, and Pony Head question whether or not Goblin Dogs are real. Together with her new friends, Kelly enjoys a Goblin Dog, though she admits she resents what she has to go through every time in order to get one. The end of the episode also reveals that Kelly has a boyfriend named Tad, a short hairy creature who hangs out in her hair. In "The Bounce Lounge", Kelly joins Star, Pony Head, and the rest of their old Bounce Crew in attempting to save the Bounce Lounge from being closed—mainly to get her mind off her recent breakup with Tad. Near the end of the episode, she and Tad get back together. In "Starcrushed", Kelly (once again separated from Tad) helps Star get her mind off her strained friendship with Marco. She is also present when Star confesses her crush on Marco to him, just prior to her return to Mewni. In "Lava Lake Beach", Kelly and Tad break up for good after a continuously on-again, off-again relationship, and Marco helps the both of them through their breakup. At the end of the episode, Marco and Kelly watch the Underworld's Soulrise together, and Kelly wishes him a happy birthday. In "Monster Bash", Kelly attends the Mewman/monster party and briefly does the "sword hand dance" with Marco. In "Stump Day", Kelly attends Star's 15th birthday party on the Mewni holiday of Stump Day, where she reveals she doesn't believe in the Stump. She tries to act as a mediator when Marco and Tom get into an argument. During the argument, she learns (to her annoyance) that Tad is still living in her hair. After the guests reconcile, Kelly dances alongside Marco. In "Booth Buddies", Kelly attends Ruberiot and Foolduke's wedding and takes Marco's dragon-cycle Nachos for a joyride. In "Divide" and "Conquer", Kelly takes part in the battle against Meteora Butterfly as one of Marco's "Marc-nificent Seven". During the battle, she finds that Tad is still living in her hair, and an argument over the matter leads to her falling to Meteora. In "The Ponyhead Show!", Kelly is Marco's co-host in the "Cooking with Earth Turd" segment on Pony Head's self-made talk show. She briefly retreats to her dressing room when Marco tells her wrestling is fake, but recovers, and invites him to cook for her family. In "Kelly's World", Kelly struggles to truly move on from her breakup with Tad when Tad keeps calling her with news about moving on himself. During Marco's visit to her home dimension, Marco helps her through her old feelings while accompanying her to return a library book. Along the way, they discover they share a passion for martial arts, and they use that skill to defend themselves from the ruthless librarian. In the end, Marco and Kelly realize they are developing feelings for each other, and they agree to help each other get over the feelings they still have for Star and Tad respectively. In "Cornball!", she and Marco provide commentary for the eponymous sport. Kelly is far more enthusiastic out of the two, knowing all the rules and plays. Kelly next appears in "A Boy and His DC-700XE", as part of the dragon-cycle riding club she and Marco both belong to (with Kelly riding a woolly variant). It is revealed in conversation that she and Marco are no longer "break-up buddies", something that she is quite bitter about (as shown when she mockingly claims Tom is going to be Marco's new "break-up buddy"). In "The Right Way", Kelly helps Star and her friends protect Monster Castle from an invading Solarian Warrior, but she is struck by its Solarian Sword and remains incapacitated in "Here to Help" and "The Tavern at the End of the Multiverse". In "Cleaved", Kelly is healed of her wounds after magic is destroyed, and she returns to her home dimension to continue her love of fighting with Jorby. When she first appears in "Goblin Dogs" hidden within her hair, Kelly shows a quiet nature even when Marco is trying to communicate with her. In "Starcrushed", it is revealed that Kelly has a love for battle, regularly sparring with Jorby. This likely stems from the culture of her species, the Wooletts, which is dedicated to battling, as shown in "Kelly's World". In "The Ponyhead Show!", Kelly is stated to be a fan of professional wrestling, until Marco ruins it for her by revealing that the sport is fake. Kelly is shown in several episodes to be skilled in sword-fighting, using both small one-handed swords and large two-handed swords. In "Kelly's World", Kelly is shown to also be skilled in hand-to-hand combat, having been taught by her father in the Woolandian martial art of wool-hair-do (similar to Earth karate), and she has above-average reflexes as a result. In the same episode, she demonstrates a two-person fighting style called "Dual Mode" with Marco. In "Lava Lake Beach", Kelly is shown to have a small pocket dimension inside her massive hair, large enough to fit Marco, Tad, and a large number of objects all at once. When Kelly's body is covered up by her hair, she bears a significant resemblance to the Addams Family character Cousin Itt. Kelly breaks up with Tad often, as she states in "Starcrushed" that they're on their third break that week. In "Lava Lake Beach", they break up for good (though Tad refuses to accept it, much to Kelly's annoyance). "Lava Lake Beach" reveals that Kelly's hair contains a pocket dimension of some sort, and that Tad has been living there. Even after they break up, Tad still sneaks back into Kelly's hair, as shown by "Stump Day" and "Divide". Kelly often meets up with Jorby to spar with each other. It is implied by Janna in "Stump Day" that Kelly may have a crush on Marco Diaz. This is confirmed in "Kelly's World" to be the case. "Divide" shows that Kelly owns many swords, including an ancestral family sword, in "Kelly's World". In "Kelly's World", Kelly is revealed to belong to a race of species called Wooletts from the Woolandia dimension. The Wooletts' culture is centered almost entirely around fighting.