Patrick is at his home preparing for the next day, which is Starfish Day. SpongeBob, who wants to go jellyfishing with Patrick, finds that Patrick is frantically cleaning up his home.
When questioned about his actions, Patrick gives SpongeBob a note, then a letter, and then a message, which states that Patrick's mother and father are coming over for the holiday Starfish Day. Patrick then gets upset, and reveals that his parents think he is "dumber than a sack of diapers" and would just think that he would be a big stupid loser. SpongeBob, who feels sorry for Patrick, offers to pretend he is dumb so Patrick's parents would think Patrick is smarter by comparison.
The next day, Patrick's parents arrive. Patrick shows them inside his house, and then SpongeBob arrives, wearing his karate helmet so he would look like a dummy. After SpongeBob meets Patrick's parents, Patrick starts to believe that SpongeBob is dumb, forgetting that SpongeBob is only pretending to be dumb.
At dinner, Patrick begins to milk the moment and make personal insults, which annoys SpongeBob. SpongeBob decides to have a talk with Patrick in the kitchen. However, the talk and reminder both fail to make its way into Patrick's narrow head.
SpongeBob confesses to his parents that he is not really a dummy, and that he was only playing the part of one so that they would appreciate Patrick more. This also fails, though, because Patrick's parents think that Patrick "taught" SpongeBob on how to talk, eat, and do the basic things in life. They all laugh, which makes SpongeBob upset, shout and crashes the wall in Patrick's house to get out.
Patrick's parents commend Patrick on his supposed intelligence, and later reveal their names, Janet and Marty. Patrick, confused and outraged, asks who they are. Before anything else can occur, Squidward comes to Patrick's house with two other starfish, Herb and Margie, and says, "Does this lovely couple belong to you? They've been standing outside my house saying "Where's Patrick?" all day! It's driving me nuts." Patrick recognizes the starfish couple as his real parents and they are happy to meet him, and said that he remembers to wear his pants. Janet and Marty then remember they do not even have a son and leave while Patrick, Herb, and Margie share a laugh.
Apparently, Patrick has forgotten how to eat in the past as evidenced by SpongeBob saying, "Patrick! You've forgotten how to eat again! Don't worry, I'll get the funnel." Patrick informs him that is not the problem, to which SpongeBob responds, "Darn, I like the funnel." In addition, an image in "Grandma's Kisses" shows Patrick feeding SpongeBob a pumpkin through a funnel.
Coincidentally, Thomas F. Wilson is also known for playing Biff in Back to the Future, while the protagonist of the film was named Marty McFly.
Marty and Janet seem just as stupid and unintelligent as Patrick is. They forgot the obvious fact that they did not even have a son, and like Patrick, they did not realize that SpongeBob was not dumb when he admitted it.
This is one of the few times a math equation (2+2=4) is shown within the SpongeBob universe. Another example is shown in "SpongeHenge" with calculus.
In Croatian dub, the episode name is "Tko je Glup?" or "Who is Stupid?"
This episode marks the first appearance of Patrick's furniture made out of sand.
The scene where Patrick goes "Huehuehuehuehueh!" has become a popular internet meme.
Patrick mistakes the word "genius" for "genies," thinking that "genius live in lamps." However, in "Christmas Who?" he says the word genie correctly.
In Indonesia, instead of saying, SpongeBob says “Patrick! You forgot how to eat again! Come on, we'll get the funnel.," SpongeBob says “Patrick! You forgot how to clean your ears again, don't worry we'll get the stick.”
When SpongeBob turns over the note, a 16th note can be seen. When he turns over the letter, the letter B can be seen.
Ennio Torresan, Jr.'s storyboard artist credit has been removed in later airings of the episode.
When SpongeBob runs into his house as a portrayal of his stupidity, Squidward's house is not there. When Patrick, Janet, and Marty are talking by the Pineapple house, Squidward's house disappears again.
When Patrick's fake parents are at his house, there is a complete kitchen and living room with sand furniture. At the end, where Patrick's real parents are laughing with him, the space under the rock is completely empty.
When Marty, Patrick and Janet are watching SpongeBob doing various things, there is a table with dinner. After Marty says that SpongeBob might be broken, the table and the food disappear.
There is an error in the captions for this episode; when Patrick is mocking SpongeBob by shouting: "I'm ready, I'm ready, I'm ready!" the captions display it as "Harmony, harmony, harmony!"
When SpongeBob is mad at Patrick, Marty, and Janet (thinking he is an idiot) he escapes by breaking the wall. The background seen from the hole is the sky; however, Patrick's house is set underground. The same mistake also occurred in "Night Light."
Even though Marty and Janet were not Patrick's parents, they somehow knew his name. It is likely that they knew him before the episode.
When SpongeBob and Patrick were talking in the kitchen, after SpongeBob sad "Patrick, I get the feeling that you think I really am dumb," Patrick is wearing the "I'm with the Dummy" shirt, but when Patrick is in the next scene, the shirt is gone.
Marty was standing on the left side of Patrick and Janet was standing on the right side of Patrick. However, when they patted him, his arm was on the right side and her arm was on the left side.
SpongeBob should have already met Herb and Margie Star because he and Patrick have been friends since infancy.
The sound of a doorbell can be heard when Patrick's "parents," SpongeBob and Squidward all show up at Patrick's house. However, Patrick's house doesn't have a doorbell.