SpongeBob is running toward Patrick's house, ready to go jellyfishing. Patrick says he'll go with him, but must put away his "secret box" first. SpongeBob asks him what's inside the box, but Patrick refuses to let SpongeBob see. Despite repeated attempts, SpongeBob is unable to get Patrick into opening the box, even after he tempts Patrick with secrets of his own.
That night, SpongeBob sneaks into Patrick's house and tries to sneak a peek while Patrick sleeps. However, due to the noise SpongeBob makes, Patrick wakes up and catches him in the act. He is shocked, and declares their friendship to be over. But, Patrick ultimately forgives him and opens the box. Inside, there is just a piece of string ("A secret string!" as Patrick describes it). SpongeBob comments on how he "should've known", but when he leaves, Patrick reveals to the audience the real secret; when he pulls the string, a secret compartment opens in the box, and there is an embarrassing picture of Spongebob the audience didn't see.
- Patrick says "Hands off, peeping Bob!", a reference to the phrase "peeping Tom".
- It is revealed that SpongeBob and Patrick's symbol of friendship is a ring that sings, "It's the best friends forever, best friends forever, ring!". When a button is pressed, it has dancing figures of SpongeBob and Patrick.
- Second time Gary speaks in English. The first was in his dream in "Sleepy Time".
- Nineteenth time Squidward doesn't appear.(but he was mentioned in the episode)
- The "embarrassing photo of SpongeBob at the Christmas Party" could be the picture from the "Nickelodeon Holiday Party" commercial or the picture taken by Squidward in "Christmas Who". Or it could be one in an offscreen Christmas party.
- Running Gag: Every time SpongeBob steps on or bounces onto Patrick's house floor, it causes a loud noise.
- When SpongeBob is telling Patrick all of his secrets, SpongeBob says "I have an overbite" as one of his secrets. This is the only episode where he himself mentions his overbite.
- When Patrick mistakes Spongebob for the Clam-burglar, it is possibly a reference to a McDonald's character, the Hamburglar.
- A lot of scenes from this episode have been used on YouTube.
- This is the first episode to use a real image as the time card instead of a drawn one.
- A small clip was used for in the TV in War of the Worlds. The title card music is the same as Opposite Day, The Paper, and Your Shoe's Untied.
- In this episode, Patrick says that he has an embarrassing photo of SpongeBob at the Christmas party, however, the city meets Christmas in a later episode, Christmas Who?
- In the scene when SpongeBob is sneaking to Patrick's house at night, Squidward's house is missing.
- The potato chip on the floor that SpongeBob stepped on is in one scene, but in another scene, it is missing.
- In this episode, SpongeBob is drawn as a lighter shade of yellow.
- When Patrick says, "And to think we joined the 'Best Friends Forever' club?!" his purple eyelids disapear.
APM music identification
- Hilo, March - Title card
- Film Fanfare A - Patrick jumps out of his rock with his secret box.
- Cierre Bob Esponja - "Hey, hands off, PeepinBob!"
- On the Beach - SpongeBob tells Patrick every single one of his gazillion secrets.
- Dramatic Climax - "...secrety secret in all secretdom."
- Like Strange - "Not even...Squidward's house!"; "Good thing he didn't pull on the Secret String revealing the Secret Compartment of the Secret Box revealing this embarrassing picture of SpongeBob at that Christmas party!"
- House of horror - Spongebob worries about what might be in the secret box.
- Tomfoolery - "How do you look into a secret box?"
- Footsteps of Horror - SpongeBob sneaks inside to Patrick's house and gets the secret box.
- Jingle Bells - "Merry Christmas, SpongeBob!"