On a Friday after school, Sue invites Jasper and Blythe over to hang out in the park, though Blythe is momentarily sidetracked as Roger stops by to pick her up. Roger presents to her a butterfly-shaped pendant—Roger took one of Blythe's designs and had it custom-made by a jeweler.
Meanwhile, the Biskit Twins agree to get some dessert to unwind and stop by Sweet Delights. While in there, they get the idea to set up a party, and they start texting each other two feet from one another as Youngmee stares in confusion. Brittany realizes that they don't have a reason to throw a party. When Whittany says it's three months until their half-birthday, Brittany decides the day should be their quarter-birthday party. Brittany requests 200 cupcakes by the following day, and Youngmee accepts. On their way out, the Biskit Twins bump into Blythe, causing them to drop their coffee. Because of that, they uninvite Blythe to their quarter-birthday party. Blythe, having no idea what just transpired, just brushes it off. Somewhat mystified at Blythe's nonchalance, they hop into their limousine to uninvite more people. The pets overhear it all from the kitchen, however. Pepper, in particular, takes offense at Blythe getting uninvited.
Youngmee tells Blythe that she needs to make two hundred cupcakes, and Blythe brings Jasper and Sue over to help out. During it all, Minka looks down from above and sees the pendant, enamored at its shininess. Youngmee, Blythe, Sue, and Jasper work into the night to make the cupcakes. Blythe, having lost her coordination, unknowingly drops her pendant into the batter in the mixer.
The next morning, Minka wakes Blythe up to see the pendant. Upon realizing it's not around her neck, Blythe checks all over her apartment, to no avail. Penny says she and the pets looked around the pet sop while Buttercream scrutinized Sweet Delights, but they couldn't find it either. Blythe concludes that she must have dropped it in the batter, and she heads to Sweet Delights to ask Youngmee to bake two hundred more cupcakes so Blythe can go through the ones made the previous day and find the pendant. Youngmee is initially hesitant but goes through with the task anyway. Unfortunately, Youngmee is just as sleepy as Blythe, and the cupcakes come out sloppy. They don't notice the difference, however and ready the cupcakes for delivery.
At the Biskit Mansion, the original batch has already arrived at the party. Brittany brings one over to her little corner and shares it with Whittany. As they tear it in half, however, Blythe's pendant falls out of it. They interpret it to be a present from their father and assume there must be more presents in the other cupcakes. As they think about getting more, they see Blythe and Youngmee replacing the previous batch with the new one and interprets the situation as Blythe sneaking in to eat all of the cupcakes. Blythe blurts out a lack of "ulterior motives" for what she and Youngmee are doing, and the Biskit Twins assume that Blythe is after the supposed gifts hidden in the cupcakes. Whittany and Brittany tugging the cupcake cart back and forth with Blythe and Youngmee to claim the old cupcakes for themselves lodges open the bottom compartment, where the pets were hiding.
One of the cupcakes rolls off, and its sprinkles sparkle in the party lights. Minka wanders off to go get the cupcake, prompting all of the other pets to leave the cart to find her. Minka proves too quick for them, and all of the pets stumble around on the dance floor. A partygoer notices Vinnie and Zoe, and the party breaks out into a panic. The security guard attempts to do crowd control but gets flung into a fountain with a shark in it. The shark bites him in the face, and he runs around screaming in pain, knocking over the cupcake cart and thus ruining all four hundred of them.
The pets return to Blythe and tell her that they're going to stomp on all of the cupcakes until they find the pendant. As they do so, the filling in one of the cupcakes Vinnie stomps lands on someone's face. In retaliation, he throws a pizza at a random person. Soon, everyone is throwing food at each other and screaming. The Biskit Twins confront Blythe saying that it's her fault, to which Blythe admits she's just looking for her pendant. Whittany holds it up showing that they have it, and Minka, consumed with rage, agilely retrieves it and gives it back to Blythe. Blythe, Youngmee, and the pets walk out, leaving the Biskit Twins to themselves in a ruined room with panicked people.
Back in Blythe's room, Blythe and Youngmee chat about how terrible the day was. Jasper and Sue drop by, however, ready to bake a cake in celebration for the meeting of the three of them. Blythe and Youngmee collapse onto the bed, having had enough of baking for the while.
This episode contains examples of (YMMV entries go here):
- 24-Hour Party People: There are a lot of attendees at the Biskit Twins' quarter-birthday party. Then again, they do claim to have lots of friends in "Blythe's Big Adventure Part 1."
- Ageless Birthday Episode: Not once is the twins' age ever brought up.
- Amazingly Embarrassing Parents: Roger munching on a candy necklace—fortunately, done in private in Roger's car.
- Attention Deficit... Ooh, Shiny!: Played literally in this episode. In Act 3, Minka abandons keeping a low profile to go grab a particularly shiny cupcake.
- Buffy Speak: The industrial mixer is called the "mixer thingy."
- Butt-Monkey: The security guard, who gets tricked by Blythe and indirectly starts the chaos in Act 3 that ends with him getting a shark bite and a fish on his head.
- Call-Back: The Biskit Twins can visualize fractions in their heads rapidly when figuring out when their quarter-birthday party would be. In Act 3, Brittany also correctly points out that there can only be two quarter-birthday parties per year. They previously demonstrated an aptitude for math in "Books & Covers."
- Chekhov's Gun: Minka being drawn to shiny objects.
- Claustrophobia: Averted with Minka this time. This may be the source of Pepper's nervousness though.
- Continuity Nod: The music playing at the Biskit Twins' last party is an instrumental version of "BFFs." They play the same song in Act 3.
- Blythe, once again, gets banned by the Biskit Twins from entering someplace. Sunil expresses anger with the background turning red, which also previously happened in "Gailbreak!"
- The montage with Youngmee and her friends in the kitchen making the cupcakes is accompanied by an instrumental version of "The Sweet Shop Song."
- Pepper points out that, due to Sunil's incompetence at magic, he couldn't have made Blythe's pendant disappear. The security guard from "Lights, Camera, Mongoose!" was also hired for the party.
- Pepper feels uncomfortable in enclosed spaces like in "Dumb Dumbwaiter," though in the cupcake cart's bottom compartment this time instead of a dumbwaiter. Minka seems just fine, however, despite exhibiting a bad case of claustrophobia in that episode.
- Vinnie, once again, is depicted as a kaiju wrecking everything in sight.
- Whittany and Brittany get food poured on their heads again.
- Contrived Coincidence: The first cupcake the Biskit Twins take for their quarter-birthday party happens to be the one with the pendant inside. They lampshade it. (See the quote at the top.)
- Eek, a Mouse!!: The partygoers' reaction to the pets.
- Exhausted Eye Bags: Jasper, Sue, and Blythe towards the end of their cupcake-baking, and Youngmee by the day of the party.
- Failed a Spot Check: Blythe suffers a series of these as she becomes sleepy, culminating in Blythe getting caught by the Biskit Twins at their party as she walks right by them without noticing them.
- Food Fight: The quarter-birthday party degenerates into one.
- Jerkass Has a Point: Brittany blames Blythe for ruining the party. She is absolutely right: Not only was the problem Blythe's fault to begin with (albeit accidentally), her trying to keep the pendant a secret caused a lot of unnecessary trouble. From their standpoint, Blythe crashed the Biskit Twins' party for no real reason.
- Jive Turkey: In the Cold Open, Roger blurts a "True dat" when Blythe says it's not her birthday.
- Kaiju: Parodied with the camera angle in the shot where Vinnie destroys the cupcakes.
- Messy Hair: Happens to Jasper, Sue, and Blythe by nightfall as they work in the kitchen. Youngmee seems unaffected, at least until the following day.
- Security Cling: Gender-inverted—a boy leaps onto a girl's arms when he sees Vinnie and Zoe.
- Shout-Out: Buttercream demonstrates the mixer with, "Follow the Buttercream Road!"
- Squee!: Both twins at Whittany's suggestion of throwing a party.
- Suspiciously Specific Denial: Blythe tells the Biskit Twins that she has no ulterior motives with bringing new cupcakes over.
- Threatening Shark: For some reason, there is a shark in the fountain in the Biskit Mansion's main hall. The security guard is no match for it.
- Wingding Eyes: Minka in Act 3 when she sees a cupcake reflecting off the party lights.