Youngmee's Aunt Christie opens a confectionery store adjacent to Littlest Pet Shop, and the pets meet pet Buttercream Sunday, a hyperactive rabbit, who invites them to overindulge themselves on the sugar-filled treats located in Christie's pantry.

Surrounded by guilt, the pets try to prove Blythe's innocence after she is accused of sending Aunt Cristie's truck careening down the street while meeting Buttercream's alley cat friend, Sugar Sprinkles.

Blythe enlists the pets to retrieve her new favorite necklace that fell inside a vat of batter used for filling a huge cupcake order with Youngmee. This proves difficult for them, when they discover the order was placed by Fisher Bisket for his twin daughter's "quarter-birthday" party.

Russell, Zoe, and Vinnie, along with Buttercream, try to retrieve a recipe stolen from Blythe by the Biskits, who plan to use it for a baking competition hosted at Blythe's school. All the while, Vinnie has a vision of cakes occupying the world.

Vinnie's tail falls off in an act of autotomy, and after a series of trials to find an adequate replacement for it, he is shocked to find that he becomes better at dancing without one. Meanwhile, Zoe and Pepper become rivals over the theme for a party meant for Penny Ling.

The host of a reality television series informs Mrs. Twombly of buried treasure located beneath Littlest Pet Shop, belonging to one of her ancestors. Their efforts at excavation quickly become the source of irritation for Blythe when they start causing property damage, and the source of outrage for Pepper, who takes the crew's map to show to the pets. There, the roots of Littlest Pet Shop are uncovered, and the story of Henrietta Twombly is told in the form of flashbacks.

Blythe must babysit Buttercream while trying to finish reading a book simultaneously, while Pepper struggles to socialize with a visitor to the day camp whom she finds herself smitten with.

The pets try to convince Minka that she is the first monkey to land on Mars, and Pepper asks Blythe for input for her stand-up comedy act.

Blythe must reveal her secret in order to save Youngmee's appearance on television and their friendship.

A massive snow storm hits Downtown City, trapping Blythe and the pets at Littlest Pet Shop and things get tense with the pets at each other's throats. Meanwhile, Roger keeps getting lost while trying to dig through the snow to get to the pet shop to save Blythe.

Blythe and the pets help Cheep-Cheep, a cousin of Minka, when he believes his scientist owner invented a helmet for pets to speak with humans.

The gang compete to tell the spookiest story. Meanwhile, Roger experiences extreme jet lag and mistakenly believes he's living out a nightmare.

Underground bunny races become all the rage and Vinnie and Sunil get swept up in the excitement, so much so that they mistakenly give away Blythe's cell phone as a prize.