What do the Wonder Pets do during their summer holidays? Join the circus, of course!

Ming Ming, Linny and Tuck aka The Wonder Pets are on summer holidays and they rescue a young circus lion named Cubby from falling off a circus train. The Penguin Ringmaster is so impressed with the Wonder Pets that he offers them all jobs at the circus! But there is one catch - the team will have to split up and do separate acts! Linny is unsure but accepts the offer when she sees how much it means to Tuck and Ming-Ming. When Cubby and his friends Baby Panda and Baby Monkey get caught on the high wire, the Wonder Pets reunite to rescue them. In the end, the Wonder Pets decide to return to their classroom, where they can be a team again and rescue animals in trouble.