Peg and Cat are in their garden, picking clovers. Peg finds a four-leaf clover and puts it in her hat for good luck. Peg is sneezing a lot and whenever she sneezes in the middle of a sentence, Cat finishes.
Peg then has a bath and is afraid because she got a call from a doctor, who said that she is probably allergic to something and that cats are a possible thing she's allergic to. Cat sits outside and begins to sing a song about how he is sad that Peg might be allergic to him, but is carried off by a bird.
When Peg finds Cat missing, she thinks he might have run away. Ramone arrives, with a helicopter that runs on 100 pebbles and they search for Cat while Peg sings a song about how much she misses him. Then, the helicopter runs out of pebbles and they land in the ocean. Peg thinks some seashells might work and starts to fill up the fuel tank. Ramone is doubtful, but the seashells work, however, they are swallowed by a whale.
It turns out, Cat got swallowed by the whale too, but everyone is all right. Peg reassures Cat that she will be his best friend even if she is allergic to him and the whale sneezes them out, so they fly home.
At home, Peg decides to test the objects in her hat to see if they make her sneeze, but she miscounts and ends up sniffing four, none of which make her sneeze. When she realizes her mistake, she sniffs the fifth item, the four-leaf clover, and turns out to be allergic to clovers. The bird and the whale then show up again and apologize, revealing that taking Cat away and swallowing Cat, Peg, and Ramone was only an accident, then they sing about mistakes with various celebrities.
This episode provides examples of:
- An Aesop: Mistakes are acceptable and normal.
- Amazing Technicolor Wildlife: Cat is indigo and the bird is stripy.
- Anachronism Stew: During the mistake song, the characters meet Albert Einstein and Marie Curie.
- Blown Upward by a Blowhole: After a whale accidentally swallows Peg and Cat, it blows them out through its blowhole.
- Cat Up a Tree: Never happens in this episode, but "getting stuck in trees" is one of Peg's things she mentions remembering Cat doing.
- Continuity Nod: The song Peg sings has a few mentions of previous episodes:
- "Getting stuck in trees" (he did that in "The Tree Problem" and "Another Tree Problem")
- "Chasing after chicks" (he did that in "The Chicken Problem"
- "Shaking it for the bees (he did that in "The Honey Problem")
- Cool Old Guy: Peg sees the elderly Albert Einstein, who she sees as amazing and a genius. Well, he is a famous scientist.
- A Dog Named "Dog": A cat named Cat.
- Einstein Hair: Einstein himself, complete with the hairdo, appears at the end.
- Friendship Song: The song Peg sings while looking for cat talks about the memories she has of things she did with him.
- Funny Animal: Downplayed for Cat, who walks on two legs and speaks, but goes naked, is the size of a real-life cat, and is otherwise pretty catlike.
- The Klutz: Tripping over things and falling on his rump is one of the things Peg remembers Cat doing in her memory song.
- The Medic: Downplayed. A doctor is mentioned, but not seen.
- Melancholy Musical Number:
- Cat sings a blues song about how he is sad about Peg possibly being allergic to him.
- Downplayed for Peg's song she sings while she and Ramone search for Cat. It does mention that she misses him a lot, but it seems hopeful too.
- No Name Given: The bird and the whale's names are not revealed.
- Plot Allergy: The main plot is about Peg being allergic to something. She's worried it's cats, but it turns out to be clovers.
- Talking Animal: The whale and the bird can talk, but they're otherwise normal animals.
- Undying Loyalty: Peg would stick by Cat even if she was allergic to him.
