- SpongeBob SquarePants
- Patrick Star
- Squidward Tentacles (mentioned)
- Squidward Tentacles' house (as a character)
- Gary the Snail
- Clam Burglar (mentioned)
In the beginning of the episode, SpongeBob runs towards Patrick's house, ready to go jellyfishing. Patrick says he will go with him, but must put away his "secret box" first. SpongeBob tries to peek inside, but Patrick refuses to let him see. SpongeBob entices Patrick by sharing his own secrets, but this only convinces Patrick to keep his secret box even more closely guarded. SpongeBob tries to distract him with many of his own secret possessions, but Patrick only pays attention to his own box.
As Patrick explains the lengths he must go to keep his box safe, he fails to notice SpongeBob sneaking off with it, giddily preparing to look. Patrick stops him just in time and struggles with SpongeBob over the box. The sight of SpongeBob's arms popping off while still desperately clinging to the box disgusts Patrick, making him question the validity of their membership in the Best Friends Forever Club.
He threatens to end their friendship if SpongeBob continues trying to look at his secret. SpongeBob begs Patrick for his forgiveness and promises to respect Patrick's right to secrecy, and they remain friends.
That night, SpongeBob cannot sleep, still thinking about Patrick's secret box and wondering about its contents. He convinces himself that sneaking into Patrick's house while he is asleep would prevent Patrick from getting upset and he will be able to look at the secret without feeling guilty. Despite Gary's admonitions, SpongeBob puts his plan into action, pulling on a silk stocking for a mask and slipping under Patrick's rock.
Inside, the box lays in full view on Patrick's nightstand. Trying to tiptoe across a floor covered in potato chips and rubber ducks, SpongeBob fears waking Patrick with every step. Finally making it to the bedside, SpongeBob reaches for the box but Patrick sleepily grabs hold of it. SpongeBob gently slips himself in place of the box just as Patrick attempts to take something from it, yanking SpongeBob's tongue in the process. Patrick then places SpongeBob next to him on the bed, allowing SpongeBob to get back onto the floor. As he prepares to leave, SpongeBob trips on his shoelace and begins crashing and bouncing around the rock in a cacophony of noise, culminating in slamming against the wall and breaking a framed photo of him and Patrick in half. Despite all of this, Patrick remains fast asleep.
SpongeBob quietly remarks how heavy a sleeper Patrick is, which causes Patrick to finally wake up and catch the masked SpongeBob with the box. Thinking him to be the Clam Burglar, Patrick prepares to assault him with a pillow until SpongeBob reveals his identity with his Best Friends Forever ring. In shock and distraught, Patrick declares their friendship to be over. Immediately afterwards, Patrick changes his mind and finally allows SpongeBob look inside the box.
SpongeBob eagerly opens the box, only to find a piece of string. Thanking Patrick for letting him look, SpongeBob heads home, laughing at how he should not have been surprised. Alone once more, Patrick demonstrates the true secret nature of the box: when the string is pulled, a secret compartment opens and reveals an embarrassing picture of SpongeBob at a Christmas party, and Patrick laughs at it, joking a Merry Christmas to SpongeBob, as the episode ends.
- Every time SpongeBob steps on or bounces onto Patrick's house floor, it causes a loud noise.
|( ‣ ) Associated production music|
|( • ) Original music|
|( ◦ ) SpongeBob music|
‣ Hilo March - The Hawaiian Serenaders [Title card]
‣ Film Fanfare (a) - Dick Stephen Walter [Patrick appears.]
• Idea Vibe - Nicolas Carr ["Secret box?"]
• SpongeBob Closing Theme - Steve Belfer, Nicolas Carr ["Hands off, Peeping Bob."]
‣ On the Beach - Kapono Beamer [SpongeBob telling Patrick all his secrets]
• Enigma Vibe 2 - Nicolas Carr [spilled milk]
• Sponge Monger - Sage Guyton, Jeremy Wakefield [SpongeBob's "secret stuff"]
• Gator - Steve Belfer [Patrick looking inside his secret box.]
• Tymp Roll - Nicolas Carr [timpani roll]
‣ Dramatic Climax - Mike Sunderland ["Nobody must know the mystery of the box!"]
‣ Like Strange - Kenny Graham ["Not even... Squidward's house!"]
• Steel Sting - Jeremy Wakefield [shot of the Best Friends Forever ring]
‣ South Pacific Island II - Victor Cavini ["I feel so filthy."]
‣ Ulkereien - Gerhard Trede ["After all, this is a pretty great secret."]
‣ House of Horror - W. Merrick Farran [SpongeBob worried about what is in the box]
‣ Tomfoolery - David Snell ["How do you look into a secret box?"]
‣ Kommissar X - Gerhard Trede [SpongeBob sneaks into Patrick's house at night.]
‣ Footsteps Of Horror - W. Merrick Farran [Patrick sleeping/Wall starts to crack/Nail falls off/SpongeBob makes a loud noise upon touching the floor/SpongeBob steps on a potato chip/SpongeBob steps making loud noises again/Patrick falls back to sleep/SpongeBob trips on a shoestring/Box lands on SpongeBob.]
‣ Danger Zone - Mike Sunderland [Patrick wakes up.]
‣ English Country Garden - Curtis Schwartz ["It's the Best Friends Forever, Best Friends Forever ring!"]
‣ Paradise Isle - Jan Rap ["How could you do this?!"]
‣ Revelation - Dick Stephen Walter [SpongeBob looks inside the box.]
• Steel Licks 10 - Jeremy Wakefield [secret string]
‣ Like Strange - Kenny Graham [Patrick laughing]
• Jingle Bells - Sage Guyton, Jeremy Wakefield [The ending.]
- This episode is available on the Halloween, Complete 2nd Season, First 100 Episodes, The Ultimate SpongeBob Box Set, The SpongeBob SquarePants Collection, SpongeBob ScaryPants Collection, The SpongeBob SquarePants 8 Season DVD Collection, Nautical Nonsense and Sponge Buddies (Danish and Norwegian only), The Houses of the Band, Band Geeks, The Complete Second Season, Holidays with SpongeBob 3-DVD Gift Set, Laugh Pack, Best of SpongeBob, Simply Patrick, From the Beginning, Pt.1, SpongeBob SquarePants Vol. 3, The First & Second Seasons, The Best 200 Episodes Ever, and SpongeBob and Friends: Patrick SquarePants DVDs and on VideoNow.
- "The Secret Box" was ranked #68 during the SpongeBob's Top 100 event in the UK and Ireland from June 4-8, 2012.
- This episode is referenced in the song "Under My Rock" from The Best Day Ever album and on The SpongeBob SquarePants Movie soundtrack.
- According to an interview with Stephen Hillenburg found here, the idea for this episode came from this quote:
"The idea came to Drymon because he, too, had a secret box as a child." "He started telling us about it. We wanted to make fun of him and use it."
- This is the first episode to use a real image as part of the title card rather than a drawn one.
- In most episodes, Patrick, being a starfish, sticks to the bottom of his rock (which is also considered the ceiling to his house) while sleeping. However, in this episode, he has a bed.
- This is the first episode to premiere during the Totally Twisted Telly event.
- This is the first episode in which Gary speaks. In "Sleepy Time," he only spoke in a dream.
- According to The Ultimate SpongeBob SpongeBash, Victoria Justice rated this episode as her favorite.
- This episode reveals that SpongeBob and Patrick have been friends since they were babies.
- SpongeBob's secrets are as follows:
- He loves his job at the Krusty Krab.
- He sleeps with his shoes on.
- He likes jelly on both sides of his toast.
- He has an overdue library book.
- He has a high opinion on jellyfishing and bubble-blowing (it is never revealed what exactly his opinion is since it is interrupted through transition).
- Something about his overbite.
- He has never been late to work.
- He had said "fancy" in conversation before.
- He likes to dance to loading zone announcements.
- He still does not have his driver's license.
- He is a little bit on the short side.
- He was wearing three pairs of underwear at the moment.
- It is revealed Squidward's house can move on its own.
- In the Polish dub, the episode's title is "Supertajne pudełko," which translates to "The Super Secret Box."
- In the 2005 movie War of the Worlds, Rachel, Tom Cruise's daughter, is shown watching this episode on TV. However, the audio and video are out of sync.
- After SpongeBob took the box from Patrick, he could've looked in the box, gave it back to Patrick, and left the rock in silence, instead of commenting on what a heavy sleeper he is. SpongeBob most likely does not expect that Patrick would instantly wake up.
- Patrick manages to sleep through all those noises, yet he wakes up when SpongeBob comments on his heavy sleeping in a barely audible whisper.
- This is one of three episodes to have just Tom Kenny and Bill Fagerbakke as the voice actors. The second is "Rise and Shine" and the third is "The Donut of Shame."
- The end of the episode is foreshadowed earlier in the episode when Patrick pulls on SpongeBob's tongue, just like how he pulls the string on his secret box.
- The French title of this episode is "La Boite Aux Secrets" or "The Box of Secrets."
- This is the third episode where SpongeBob is revealed to have shoes with shoelaces. The first was "Rock Bottom and the second was "Your Shoe's Untied."
- When SpongeBob sees the string, upon close inspection the farthest end appears to be fastened to the box, foreshadowing its function.
- When the picture of SpongeBob and Patrick splits into two halves, with SpongeBob on one half and Patrick on the other, it foreshadows the consequences of stealing the secret box following the moment Patrick wakes up, and the imminent end to their friendship due to the distrust SpongeBob is giving his best friend.
- In this episode, SpongeBob says he was never late for work. However, in "Hooky," he was late.
- Whenever Patrick opens his secret box, he does not pull the string to open the secret compartment; instead he just looks in the box and laughs.
- He might've done this deliberately to deceive SpongeBob (and the audience) into not learning the real secret.
- Patrick says "Hands off, peeping Bob!," which is a reference to the phrase "peeping Tom."
- SopngeBob's line, "What's in the box?!" is a reference to the movie Se7en.
- Patrick mistakes SpongeBob for the Clam-burglar, a parody of the McDonald's character Hamburglar.
- When SpongeBob sneaks over to Patrick's house, Squidward's house is missing.
- The potato chip on the floor that SpongeBob steps on is present in one scene, but in subsequent scenes, it is missing.
- When Patrick says "And to think we joined the 'Best Friends Forever' club?!," his lips don't sync.
- Also, his purple eyelids disappear.
- After SpongeBob's arms come off, Patrick grabs what appears to be SpongeBob's right arm to point to him with. But when he is pointing at SpongeBob with the arm, it becomes the left arm.
- Before Patrick mentions Squidward's house, SpongeBob has double the freckles on his cheek than he normally does.
- When SpongeBob gathers the "secret" stuff, he goes towards Patrick's house, not his own.
- When the screen shakes, there is a light blue border.
- In the opening credits, the 'k' in Carson Kugler's name is lowercase instead of capitalized.
- Erik Wiese's surname is also misspelled as "Weise."