Joy Hyung is a supporting character in Barbie: Skipper and the Big Babysitting Adventure. Joy has a summer job working at a beach snack bar. She sings while she works. Skipper and Tammy are customers. Tammy is rude and demanding while making an order, so Skipper speaks up for Joy. Joy forgets to put the lid on a smoothie blender properly, so the smoothie ends up going on Tammy and Joy gets fired. Later, Joy thanks Skipper for speaking up for her. Joy wants a recording contract because she loves to sing, and Skipper loves to DJ, so the girls bond over their love of music and lack of summer jobs.
A guy with a sandwich board gives an address for Joy and Skipper to get summer jobs. Upon arriving, Joy sees it is the Oceans Extreme water park. Joy thinks it will be the best summer job ever. At the interview lobby, Joy feels intimidated by the atmosphere and other interviewees odd behavior. Joy and Skipper meet a girl named Anna. Skipper gets interviewed and finds out the boss is Barbie's rival Tammy, whose father Milton owns the park. Milton hires Skipper against Tammy's wishes, and he also hires Joy and Anna.
Outside the park, Joy and Anna are excited they have jobs. Tammy dislikes Skipper so Skipper doesn't want to work with her. Joy says they are in it together. The girls meet Cheri, and Anna recommends Cheri get a job at Oceans Extreme. The girls all start working there the next day. Skipper helps Joy at the snack bar. They give away ice cream for free, but the kids spend money on other items. Milton is so impressed that he gives Joy and Skipper the afternoon off. They visit Cheri at the doggy day care and she says working there is a dream come true. Joy replies that her dream is to play a huge concert.
One day, Milton makes Skipper employee of the week. Joy applauds as Skipper collects her award. Skipper suggests the park have a day care for little kids, and Joy nods in agreement. Skipper privately tells Tammy they could rent a gaming bus for the day care. Tammy plans on telling Milton that Skipper got bad reviews for babysitting. Tammy demands that Skipper clean an extremely dirty pool, and then she steals Skipper's gaming bus idea. Skipper quits. As she leaves the park, she sees that Joy, Cheri and Anna were coming to help her clean.
Cheri and her friends get on the gaming bus before Tammy has paid for it. Joy sings karaoke. The bus jolts, causing Joy and her friends to realize the bus is moving. The driver, Pete, got tired of waiting for Tammy to pay him and drove away, not knowing anyone was on the bus. Skipper makes a plan to distract the kids until they can ask the driver to bring them back to the park. Skipper refers to herself, Cheri, Anna and Joy as "Skipper's Super Sitter Squad" and they cheer. Pete drives the bus to a parking lot, gets into a car and drives away. Joy and her friends yell at him to stop, but he doesn't hear them.
Skipper phones Tammy, and Tammy says she will send her limo. Suddenly, a kid named Erica goes missing. Joy helps search for Erica until Skipper finds her. A sandstorm begins, so Skipper tells everyone to hold hands. Joy holds hands with two kids and Skipper says they will find an adult and ask for help. After the sandstorm ends, the kids see an auto-piloted party plane and run towards it. Joy and her friends fall down as they chase the kids. A flight attendant lets the kids on the plane because she assumes the kids are voluntary testers for the first flight.
Joy and her friends board the plane to get the kids, but Erica presses a button. It sends a signal for the plane to take off. Joy gets airsick during the flight. When it lands, Joy has to be helped off the plane by Cheri. They get in the limo and Joy feels sick again. The limo gets stuck in traffic by the beach. Tammy urgently needs to get the kids back to the park before their parents pick them up, so she sends a boat. On the boat, Joy gets seasick. It is too foggy for the boat captain to see, so Skipper asks some dolphins to guide the boat back to the park. Joy and her friends run back to the park and get back in time for the kids to be picked up by their parents.
Milton doesn't want to open a gaming bus day care because it will cost money. Tammy convinces Milton to let her open a day care, so Joy and her friends cheer. Milton says it can't be a gaming bus, so Joy and her friends are disappointed. Skipper and Tammy suggest that everyone work together to clean the dirty pool and then turn it into a day care. Milton agrees. Joy and her friends have a group hug with Tammy. Tammy ends the hug and says they should have boundaries. After the day care is open and successful, Joy performs for everyone and sings about her friends.
