Pete and his friends must solve a mystery when some of the cupcakes they have backed for a party go missing!

Twins Carlos and Carmen want to make Mother's Day special, and the day is going well--until they try to make cupcakes without following the recipe.

While longing to return to life in New York City, thirteen-year-old Penny helps her mother and grandmother run a cupcake bakery in Hog's Hollow, tries to avoid the beastly popular girls, to be a good friend to quirky Tally, and to catch the eye of enigmatic Marcus.

Four-year-old Babymouse wants to replace the cookies her mom prepared for Santa with a special batch of her own pink-frosted cupcakes.

Wanting to pay for her junior bridesmaid dress herself, Emma quickly finds herself challenged with not enough time to keep up with her various part-time jobs.

Juliette invites the cupcake club girls to London to cater her boyfriend's West End acting debut, and while there Lady and Lord Wakefield ask them to build a cupcake London Bridge for their daughter's birthday.

The Cupcake Club learns that good leadership is a huge part of running a successful business-and friendship is the icing on the cake! Alexis is the clear leader of the Cupcake Club: She's organized, punctual, and happy to take on the stuff like scheduling, budgets, invoicing, and the things that the other girls don't really want to do. In other words, the "unfun" things. But one day Alexis feels particularly unappreciated and informs the Cupcake...

"Klondike isn't supposed to eat the cupcakes until his sister's birthday party ... but can he wait that long?"--

Emma's younger brother Jake has tonsillitis and makes life difficult for Emma, while the Cupcake Club girls are spoiling him with cupcakes and little gifts.

Hayley's life hasn't exactly been a piece of cake, and now there's even more change in store: an adorable new puppy, a possible new school, and a new baking challenge--a wedding cake for her grandmother's big day!