Encyclopedia SpongeBobia
Encyclopedia SpongeBobia

"Knock Knock, Who's There?" is a SpongeBob SquarePants episode from season 12. In this episode, SpongeBob watches Mr. Krabs's house while he's away and goes to extreme measures to prevent burglary.



The episode begins at Mr. Krabs and Pearl's house, where Mr. Krabs is shown instructing SpongeBob on what to do while house sitting for him, since Mr. Krabs will be at a fast food convention all night. He tells SpongeBob to lock the windows, always keep a weapon on his person and to not step foot into his bedroom. Mr. Krabs hands SpongeBob a baseball bat, but SpongeBob accidentally hits himself with it, making Mr. Krabs throw the bat away. Mr. Krabs further explains that Pearl is staying with friends, and that SpongeBob will be all alone. He then warns that the neighborhood has seen a spike in robberies recently, and orders SpongeBob to not answer the door for anyone. As Mr. Krabs leaves, he tests this by knocking on his own door as SpongeBob answers, but SpongeBob realizes his mistake and slams the door in Mr. Krabs' face, much to Krabs' satisfaction. In the next scene, SpongeBob is seen checking around the house, making sure there are no robbers about. He then notices Mr. Krabs' bedroom, and suspects that burglars might be hiding, but remembers that he is not allowed to set foot in there. To get around this, SpongeBob ties a balloon to his nose. While searching through Mr. Krabs' bedroom, SpongeBob finds money under his pillow, a music box with a Mrs. Puff figurine, a bottle of cologne called "Midnight Pincer," and a knot collection. SpongeBob suddenly hears a doorbell, and assumes it's the pizza that he ordered earlier. SpongeBob tells the delivery boy to slide the pizza into the mail slot, since he isn't allowed to open the door.

Meanwhile, Mr. Krabs arrives at the Fast Food Founding Fathers building, (or F.F.F.F.). The doorman asks Mr. Krabs to pay 10 cents as an entrance fee, but Mr. Krabs thinks 10 cents is a ripoff and decides to go home. As Mr. Krabs is taking off, he overhears another fish winning 1,000 dollars for being the 100th person to enter the building, much to his shock. Back at Mr. Krabs' house, SpongeBob is seen watching TV, but when a horror movie comes on, he turns off the TV in fright. Just then, a knock is heard at the door, and SpongeBob approaches cautiously. It is Mr. Krabs, who cannot enter his house because he forgot his keys. SpongeBob does not believe him, however, as he thinks that Mr. Krabs is still at his convention. SpongeBob admits that the "robber" sounds like Mr. Krabs, but looks nothing like him (due to the door's peephole distorting Mr. Krabs' appearance thus making him look different). Mr. Krabs attempts to get in through the mail slot, but fails due to him being too big. He then notices that the top window is open, and starts climbing on the side of his house in order to reach it. In a frenzy, SpongeBob calls Patrick on the phone and asks him to come over to Krabs' house, due to thinking the "burglar" is trying to break in. Patrick arrives shortly, and is able to enter the house via the mail slot, due to him having no bones and being completely made out of blubber. At the same time, Mr. Krabs is able to approach his window, but is struck down by lightning. SpongeBob and Patrick decide to start setting up traps for the robber.

In the next scene, we see that Mr. Krabs' house is filled with booby traps, such as pillows being hung from the ceiling, and a bucket of warm water being set under the window. They hear glass breaking, and prepare all the traps for use. Mr. Krabs tries to break in through the window, but is sprayed in the eyes by his own perfume, and lands in a puddle of mud. Afterwards, Mr. Krabs tries to enter his house via the toilet (while still covered in mud), but SpongeBob is able to intercept him and flush him back down the toilet using a plunger. Once again, Mr. Krabs tries breaking in, this time through his pet door, but is nearly sliced up by "sharp" cheddar. SpongeBob and Patrick celebrate their victory over the robber by watching a tough guy action movie on TV. At the same time, though, Mr. Krabs has had enough and decides to use a giant wrecking ball to break into his own house, and SpongeBob and Patrick are unaware of this due to the sound effects in the movie. Mr. Krabs finally manages to break in, but is trapped inside of a laundry basket held down by a cinderblock. At this point, Mr. Krabs gives up and starts crying, handing SpongeBob and Patrick his ID card to prove he's the real Mr. Krabs. SpongeBob and Patrick realize their mistake and let Mr. Krabs out of the trap. Mr. Krabs isn't mad at them, however, due to SpongeBob actually following his orders. After the trio exchange a hug, they hear more knocking at the door. It's Pearl, who also forgot her keys, but Mr. Krabs doesn't believe her (due to, once again, the door's peephole distorting Pearl's appearance). SpongeBob and Patrick are prepared to set up more traps, and Pearl is seen still banging on the front door, as the episode ends.

Running gags

  • SpongeBob spraying the bottle of cologne.
  • Mr. Krabs trying to sneak into his own house, only to fail and get booby-trapped each time until the end.


The episode was confirmed by Vincent Waller on June 29, 2019.[4]



 ) Production music
 ) Original music
 ) SpongeBob music

  Ahoy Landlubbers - Michael Bolger, Nicolas Carr [Title card]
  Mister Wobble - Jack Jordan [Opening at Mr. Krabs' house]
  Hot Steel and Slide Licks 40 - Jeremy Wakefield ["I've got me private things in there."]
  Laughter Trombone - [ProjectSAM Symphobia Colours: Animator] [Krabs giggles and coughs]
  Mister Wobble - Jack Jordan ["Now Pearl is staying with friends, so you'll be here all alone."]
  Laughter Muted Trumpet - [ProjectSAM Symphobia Colours: Animator] [SpongeBob's arms deflate]
  What's This - Nicolas Carr [SpongeBob's hands are back]
  Mister Wobble - Jack Jordan [Krabs orders SpongeBob not to open the door of his house for anyone]
  Hot Steel and Slide Licks 23 - Jeremy Wakefield [SpongeBob sighs]
  Melodramatic Moments - Michael Bolger, Nicolas Carr ["I told you not to open the door... for anyone!"]
  Mister Wobble - Jack Jordan [SpongeBob hits Krabs while closing his door]
  Bubble Popping Boys - Nicolas Carr, Barry Anthony [SpongeBob checking Krabs' house for signs of robbery]
  Victory Chords - [ProjectSAM Symphobia Colours: Animator] [SpongeBob sees Krabs' bedroom's door open]
  Bubble Popping Boys - Nicolas Carr, Barry Anthony ["Hmm... Mr. Krabs' bedroom. I don't remember his door being a jar."]
  Flashback - Nicolas Carr [SpongeBob remembering Krabs' advice]
  Mister Wobble - Jack Jordan ["Do not step foot into me bedroom!"]
  Hot Steel and Slide Licks 2 - Jeremy Wakefield ["Don't worry, Mr. Krabs. I won't step foot in your bedroom."]
  Tricks and Traps - James McConnel [SpongeBob checking Krabs' bedroom without stepping foot]
  Sylvia Celesta - Leo Delibes, Frederic Sans [SpongeBob discovers a music box with a Mrs. Puff figurine inside]
  Full of Beans - Robert Schreier [Closeup of Krabs' Midnight Pincer perfume]
  Sylvia Celesta - Leo Delibes, Frederic Sans [SpongeBob sprays himself with the Midnight Pincer perfume]
  Tricks and Traps - James McConnel [SpongeBob pulls the string off Krabs' knots collection]
  Drama Link (F) - Hubert Clifford [SpongeBob screams]
  Kalua Jubalee - Sage Guyton, Jeremy Wakefield [Pizza deliver slides the pizza through Krabs' mail slot]
  Handy Pandy - Cedric Palmer [Krabs arrives at the Fast Food Founding Fathers convention]
  Film Fanfare (a) - Dick Walter [Fish wins thousand dollars for being the 100th person to enter at the F.F.F.F. convention]
  Beautiful People (A) - David Walter, Dick Walter [First TV channel]
  Acrobats and Clowns A - Alfi Kabiljo [Second TV channel]
  Unknown Track 69 - ? [Third TV channel]
  Teenage Kicks - Bert Weedon [Fourth TV channel]
  New Threat - Roger Roger [Valentino] [SpongeBob watching a horror movie at Krabs' house]
  Punctuations - Ralph Dollimore [SpongeBob hears someone knocking the door]
  Comedy Punctuations And Bridges 3 - Fredric Bayco ["Open up! I forgot me keys!"/Krabs tastes cheese remains on the mail slot/"Or was made out of cheese... Oh..."]
  Stool Pigeon - Kenny Graham [SpongeBob thinks Krabs is actually a robber]
  Alone And Lost - Norman Dane [SpongeBob calls Patrick for help]
  Capering Clowns - Max Saunders [Krabs sees Patrick entering his house]
  Nude Sting - Nicolas Carr [Closeup of Patrick's blubber body]
  Crime And Danger Sign #2 - Hans Conzelmann, Delle Haensch [SpongeBob thinks the robber is trying to break into Krabs' house]
  Tricks and Traps - James McConnel [Mr. Krabs is struck by lightning and falls on the ground]
  Crime And Danger Sign #2 - Hans Conzelmann, Delle Haensch ["The robber doesn't sound like he's gonna give up."]
  Comical Clowns - Ronald Hanmer [SpongeBob and Patrick setting traps for the "robber"]
  Crime And Danger Sign #2 - Hans Conzelmann, Delle Haensch [Krabs breaks a window to get inside his house]
  Full of Beans - Robert Schreier ["Smells so wonderful..."]
  Crime And Danger Sign #2 - Hans Conzelmann, Delle Haensch ["...but it burns!"]
  In Disguise Wah Trumpet - [ProjectSAM Symphobia Colours: Animator] [Krabs is muddy]
  Bad Slide - [ProjectSAM Symphobia Colours: Animator] [Patrick hits Krabs with a pillow]
  Lap Steel - Nicolas Carr [Transition to next scene]
  Fraidy Cat - Fredric Bayco [Krabs tries to enter his house through the VC]
  Hot Steel and Slide Licks 1 - Jeremy Wakefield [Transition to next scene]
  Fraidy Cat - Fredric Bayco [Krabs tries to enter his house through the pet door]
  Dramatic Cue (D) - Ronald Hanmer [Giant cheese falls cutting Krabs' eyelashes]
  Vibe Q Sting - Nicolas Carr ["Hmm... Cheddar."]
  ? - Nicolas Carr [Rimshot]
  Eight Dramatic Bridges - Ronald Hanmer ["That's it! Time to wreck this ball!"]
  Another Goofy Cue - Nicolas Carr, Barry Anthony ["No Mr. Krabs-impersonating robber will ever get into this house with us on the job."]
  First In Command - Gregor Narholz [SpongeBob and Patrick watching an action movie on TV]
  Hot Steel and Slide Licks 23 - Jeremy Wakefield ["Wow! 3D!"]
  Eight Dramatic Bridges - Ronald Hanmer [Krabs approaches injured and angrily to SpongeBob and Patrick]
  Hot Steel and Slide Licks 8 - Jeremy Wakefield [Krabs shows SpongeBob and Patrick his ID to prove that he's really him]
  Ahoy Landlubbers - Michael Bolger, Nicolas Carr ["I can't be mad at you for following me orders."]
  Punctuations - Ralph Dollimore [Krabs thinks Pearl is actually a robber]
  Sylvia Celesta - Leo Delibes, Frederic Sans [Ending]
  Alp Horn Yodeler Guy - Nicolas Carr ["Are those me private things?"]
  Sylvia Celesta - Leo Delibes, Frederic Sans [Ending]




  • This episode was paired up with a rerun of the Kamp Koral: SpongeBob's Under Years episode "Sugar Squeeze" during the original American airing, but it currently airs with the episode "Pat Hearts Squid."
    • The episode was later paired up with "Under the Small Top."
    • This is the first episode to premiere and not be paired with another episode or its sister since "The Krusty Slammer."
    • This episode was paired up with "Plankton's Intern" on its premiere day.
      • When this episode premiered in Latin America it was paired up with "Patrick's Tantrum," while in Central and South America it was paired with "Plankton's Intern."
  • This episode previously held the record for the least amount of viewers of the series with only 0.34 million viewers. It was later surpassed by "Say Awww!" and "Patrick the Mailman" which had 0.32 million viewers.
  • This episode was released digitally in Dish on Demand on September 27, 2020, nearly seven months before airing on American television.
    • This episode was released in Optimum on Demand on December 19, 2020, along with its sister episode, five months before airing on American television.
    • This episode was released in Fios on Demand on December 26, 2020, along with its sister episode, five months before airing on American television.
    • In addition, this episode was released on The Complete Twelfth Season DVD on January 12, 2021, three and a half months before airing on American television on April 23, 2021.
  • The title card misspells the episode by improperly placing the comma after the first "Knock" instead of the second one.
    • That misspelled title was also used in the episode selection screen of Disc 3 on The Complete Twelfth Season.
  • This is the tenth episode to have a question mark in its title, the previous ones being "Christmas Who?," "Can You Spare a Dime?," "Have You Seen This Snail?," "What Ever Happened to SpongeBob?," "Hide and Then What Happens?," "Are You Happy Now?," "What's Eating Patrick?," "Goodbye, Krabby Patty?," and "Sportz?"
  • When SpongeBob pulls on a loose string on one of Mr. Krabs' knots, the entirety of his knot collection comes undone, which is a callback to "The String."
  • A clip from this episode was used in a promo on Nicktoons Global.[5]
    • Another clip from this episode was used in a promo for a Patrick marathon on November 14, 2020 and with a new episode of It's Pony.[6]
    • Two clips of Mr. Krabs getting sprayed and hanging on a wrecking ball for a Mr. Krabs marathon on November 21, 2020.[7]
    • A clip of SpongeBob calling Patrick on the phone, hiding under the table was used for 52 (53) times the show got way too real on the official SpongeBob SquarePants YouTube Channel on December 4, 2020.[8]
    • The following month, two clips were used in a New Years Day 2021 promo on Nickelodeon.[9]
  • The live-action mouth SpongeBob makes while calling Patrick returns for the first time since "Mermaid Man & Barnacle Boy VI: The Motion Picture."
  • The portrait of the snail that looks like Gary which is hung in SpongeBob's living room appears in Mr. Krabs' house.
  • This episode reveals that Mr. Krabs is an organ donor.
  • Mr. Krabs is revealed to own a figurine of Mrs. Puff which is kept in a small blue treasure chest, which dances on a cake.
    • He's also revealed to have a bottle of cologne called "Midnight Pincer."
  • This is the fifth episode where SpongeBob imitates Mr. Krabs. The first was "Gone," the second was "Mimic Madness," the third was "SpongeBob in RandomLand," and the fourth was "Boss for a Day."
  • Mr. Krabs is revealed to have a sliding pet door at the back of his house.
    • In addition, this is the first episode to show what the backside of Mr. Krabs and Pearl's house look like.
  • SpongeBob flips through the channels to see live-action footage of a yellow fish, a coconut tumbling down the hill, a wrestling match between two humans, and a black-and-white horror film involving a fish hook.
  • The Conch Shell makes an appearance in the episode.
  • The fish guy getting cash from the doorman after giving him a penny is what happens at the Krusty Krab in the episode "Clams."
  • "Hot Steel and Slide Licks 23" plays for the first time since "High Sea Diving."
  • This is the second episode where SpongeBob and Patrick mistake Mr. Krabs for someone or something he is not. The first was "My Two Krabses."
    • Ironically, both episodes are from season 12, and are before and after each other in production and episode order.
      • It is also third time that SpongeBob mistake Mr. Krabs for someone or something he is not, the first episode that is not from season 12 is "Imitation Krabs."
  • Irony: Mr. Krabs told SpongeBob not to open the door for anyone, but when he returns, SpongeBob doesn't open the door for Mr. Krabs.
  • When SpongeBob checks his feet, he makes a very similar face to the one he made in "Just One Bite."
    • The close up of SpongeBob's eyes when looking at Mr. Krabs' mouth is similar to the close up in "Hooky."

Cultural references

  • The title of this episode references the first two exchanges between the teller and recipient of a knock-knock joke.
  • The booby traps are a reference to the Home Alone movie series.
  • The "sharp cheddar" used for the pet door is a reference to the guillotine; it even makes a sound closely related to the guillotine.


  • In one scene, SpongeBob's eyelashes disappear.
  • After SpongeBob throws the remote, his bucket of popcorn, and his blanket in a frightened response, they are nowhere to be seen in the living room afterward.
  • When SpongeBob licks the pizza of the mail slot, there are two small speck of pizza that he does not lick, yet it disappears anyway.
  • At the start of the episode the door doesn't have a mail slot, but in the pizza scene it suddenly has one.

English title card in Hebrew dub for a frame.

  • In the Hebrew dub, the English title card was accidentally shown for a frame.