Original air date: December 4th, 1992
At Bon Bon's house, she and Clover are baking, and her mother walks into the kitchen. She is displeased by the mess and reminds Bon Bon to study for the math test tomorrow, warning her that she'll have to give up cooking if she doesn't do well on the test.
The next day during the test, Bon Bon cheats by looking at a note taped to her hoof. On the way home, Teddy passes her and brags that he probably got an A despite not studying. Guilt-ridden, Bon Bon writes in her diary about her cheating, but accidentally leaves the diary on the bench, where Teddy takes it.
At Starlight's ice cream shop, Bon Bon realizes her diary is missing. Her friends agree to help her look for it, but the search is ultimately unsuccessful. The next day, Teddy encounters Bon Bon and reveals he has her diary. He refuses to give it back and blackmails her into carrying his bag to school for him. He makes a list of further demands, ending with one that she goes to the dance with him.
At home, Bon Bon's mother is happy that Bon Bon did well, but can't understand why Bon Bon is crying. Bon Bon phones Sweetheart, who figures out that Teddy has Bon Bon's diary. Sweetheart in turn phones Teddy and has a talk with him about secrets, with the implicit threat of telling everyone Teddy has a teddy bear if he doesn't return Bon Bon's diary.
The next day, Teddy is going to tell Bon Bon something, but Bon Bon isn't interested. She confesses to Miss Hackney that she cheated so Teddy can't blackmail her anymore, only to discover Teddy already returned the diary to Miss Hackney, who doesn't fail her on the spot but instead has her retake the test after school.
After school, Bon Bon gleefully announces to Teddy that she got a C+. Teddy apologizes for everything and says he can't go to the dance because his father grounded him for getting an F on the test.
"Bon Bon's Diary" provides examples of:
- An Aesop: Academic dishonesty is wrong and unrewarding.
- Bait-and-Switch:Starlight: Here you go, Bon Bon! One triple decker supreme with a cherry. It's usually two jangles, but for you, one of my best friends... two jangles.
- Beware the Nice Ones: Sweetheart is the sweetest one of the group, yet the moment she figures out that Teddy took Bon Bon's diary, she immediately calls him and proceeds to very subtly threaten him to reveal his biggest secret unless he gives it back, all while maintaining her trademark cute smile the entire time.
- Blackmail: Teddy gets ahold of Bon Bon's diary, reads it, and makes her carry his bags for him and tries to make her attend a dance with him.
- Blackmail Backfire: Teddy threatens to show Miss Hackney the entry in Bon Bon's diary that says she cheated in the test unless she goes to the school dance with him, but is stopped by Sweetheart threatening to reveal his Unmanly Secret.
- Cheaters Never Prosper: Bon Bon cheats on her math test. Not only does she feel guilty about it, but Teddy gets ahold of her diary and uses it to blackmail her.
- Closed Door Rapport:Bon Bon's mother: Bon Bon, are you alright? If you got an A on your test, why are you crying?Bon Bon: Because... because I'm so happy! (cries some more)
Bon Bon's mother: Well, try not to be quite so happy, alright, dear? (walks away) - Continuity Nod: Roll-A-Rama reappears.
- Cuckoo Clock Gag: When the school’s cuckoo clock goes off after the math test, Patch rolls her paper into a pea shooter, and shoots the cuckoo off the clock.
- Easily Forgiven: Once she has her diary back, Bon Bon is rather quick to be nice to Teddy after everything he did, offering to study alongside him and bake him some cookies and even asking if he still wants to go to the dance with her.
- Eek, a Mouse!!: Patch mentions during the song how she almost fainted at the sight of a mouse, and fell over from shock, straight into her friends.
- Fear Song: "Secrets", where the girls are afraid at the prospect of someone discovering their secrets.
- Helping Another Save Face:
- When Bon Bon loses her diary, her friends all pitch in to search for it, knowing they wouldn't want someone discovering their secrets.
- Later, when Sweetheart realises Teddy has Bon Bon's diary, she forces him to give it back unless he wants her to let everyone know he has a teddy bear.
- Laser-Guided Karma: On top of Sweetheart threatening to reveal him having a teddy bear if he doesn't give Bon Bon back her diary, Teddy is grounded by his father for getting an F on the test, so he can't go to the dance he was going to blackmail Bon Bon into attending with him.
- Not so Dire: Invoked by Teddy:Teddy: Miss Hackney?Miss Hackney: Yes, Teddy?Teddy: I found something you might want.Bon Bon: Oh no!Miss Hackney: And what is it, Teddy?
Teddy: Your eraser. (smirks at Bon Bon) - One-Episode Fear: Patch is revealed to have fainted at the sight of a mouse. Notably, the presence of an out-of-control frog in the previous episode didn't frighten her at all.
- Poor Communication Kills: If Bon Bon hadn't rebuffed Teddy before she confessed to her cheating to Miss Hackney, she would have known Miss Hackney had her diary and Bon Bon wouldn't have needed to confess.
- Secret Diary: Bon Bon's is the driving force behind the plot.
- You Are Grounded!: Teddy is grounded by his father for getting an F on the math test.
