The French Narrator introduces another SpongeBob SquarePants special, hosted from Encino, California as it was 100 million years ago. From his cave-house, Patchy the Pirate, in a caveman costume, is introducing prehistoric times and talking about how great they were. However, Potty, in a futuristic robot costume, appears and says that prehistoric times were "lame" and the future is "where it's at". They begin arguing over whether SpongeBob himself likes prehistory or the future better, and while working at the Krusty Krab, SpongeBob feels a disturbance, and tells Mr. Krabs that "I've got the strangest feeling that somewhere a pirate and parrot are arguing about me. And, the parrot is winning." As Patchy and Potty continue to argue, Patchy begins the SpongeBob episode.
The cartoon features prehistoric versions of SpongeBob, Squidward and Patrick, named "SpongeGar", "Squog" and "Patar", respectively. SpongeGar, who is sleeping in his pineapple-shaped cave, is awakened by a distant herd of monstrous purple creatures, who produce a sound identical to that of SpongeBob's alarm clock that knocks the rock on SpongeGar. SpongeGar takes his version of Gary, who is bigger than the prehistoric pineapple itself, out for a walk, and he leaves a slime trail all over Squog's front yard. Squog comes out to complain to SpongeGar, but slips on the slime trail, sliding into Patar's rock, awakening its occupant, and eventually crashing back into his own house. SpongeGar and Patar begin to play, and SpongeGar uses a hollow log to blow a bubble. It then starts raining, and eventually lightning strikes the log, setting it on fire. The three experiment with it, and soon realize that it can be used to cook food, and begin cooking various items with it, including flowers, the top of a mushroom, a kelp reed, a wood stick (Patar eats it), a prehistoric ancestor of Eugene H. Krabs, seaweed flowers that look similar to corn on the cob, a green plant that looks like spaghetti, rocks that take the form of popcorn, and a krabby patty made of sand.
Over the commercial break, Patchy and Potty continue to fight, now keeping score between the future and the past. Patchy brings in a real live caveman, but Potty brings in a futuristic robot who begins repeatedly shooting the caveman with lasers.
At the end of the day, SpongeGar, Patar and Squog start fighting over whom will keep the fire. They continue fighting until it starts raining again, putting the fire out. SpongeGar and Patar apologize to each other for fighting, but Squog blames them for putting it out and attempts to hit them over the head. Before he can do so, however, lightning strikes him and SpongeGar and Patar cook marshmallows over his charred body.
After the cartoon, Patchy is shown sitting outside his cave, apparently having lost to Potty. However, Potty comes outside and invites him back in, where Cavey the Caveman and the Robot Android Cyborg DX-294888 do a rap called "When Worlds Collide". The song montage features scenes from SpongeBob B.C. and "SB-129". The episode ends with Potty giving Patchy a "gift": a Tyrannosaurus Rex, which begins chasing him as Patchy says bye to the viewers.
SpongeGar, Patar and Squog speak in a primitive language similar to English. Many words and sounds are taken from or based on English words/sounds.
"Ugh" was ranked #16 during the Best Day Ever event on November 9–10, 2006.
Millions of years before the present
This is the first episode where normal SpongeBob appears as a cameo. The second is "Rise and Shine."
This is the first episode to show clips from other episodes. The second is "The Sponge Who Could Fly" during the "Remembering SpongeBob" sequence.
Squog says: "Wait a minute" at one point, the only English sentence spoken by any of the Cavemen.
Scenes from "SB-129" are seen during the "When Worlds Collide" sequence.
One of the foods SpongeGar cooks is a Krabby Patty replica made of sand.
The caveman that Patchy found and thawed out is played by Bill Fagerbakke, who voices Patrick. Incidentally, Potty's robot is voiced by Tom Kenny, the actor of SpongeBob and Patchy.
In original and DVD captions, the lines where the characters are speaking cave-ish are listed as "speaking gibberish" or "gibberish" in the dialogue. Example: SpongeGar's line "Banooga ready!" (which means "I'm ready!") is written as "(speaking gibberish) Ready!"
The opening credits on the title card are also unique. This is the third time this has happened, the first two being SB-129, and "Krusty Krab Training Video."
One of the singers in the barbershop quartet is a woman wearing a fake moustache.
The music used in the introduction of SpongeGar, Patar, and Squog is exactly the same music used in the title card of the episode Rock Bottom.
Running Gag: Patar putting salt on items and then eating them.
Excluding the narrator, none of the dialogue in the SpongeBob episode were edited in the Korean version.
"When Worlds Collide" is the only rap on "SpongeBob SquarePants".
The atonal singing of the barbershop quartet is a reference to the piece "Requiem for Soprano, Mezzo Soprano, Two Mixed Choirs, and Orchestra" by György Ligeti, which was used in the film 2001: A Space Odyssey whenever the monolith appeared.
The scene in which SpongeGar realizes that he can use a stick as a tool to take a piece of coral out of the fire pays direct homage to the Dawn of Man sequence from the film 2001: A Space Odyssey, a famous scene in which a group of apes learn to use a bone as both a tool and weapon. In both cases, the narrative is portrayed these stories without the use of conventional dialogue (using nonsensical cave-ish speech in Ugh and using ape noises in 2001. The music is also a direct homage, with a modernistic wailing piece composed by György Ligeti used while SpongeGar makes his discovery, and the classical piece "Also Sprach Zarathustra" by Richard Strauss played after SpongeGar's discovery, mirroring the use of those same two pieces of music in 2001.
B.C. being "Before Comedy" is a parody of what it actually is, "Before Christ."
When Patar punctured his lip, the stick is thick, but when SpongeGar stomps on a little crab take out the stick out of Patar's lip and impaled a little crab and give him to it; the stick is thin.
When Gary gets a snail trail on Squog's rocks, it is on the one closest to his house, but when Squog looks out the window, it is on the third one from his house.
Squog doesn't have a door on his house until he takes the fire to it.
The original captions spell Patar's name as Pathar.
The YTV captions spell Squog's name as Squd.
Patchy has brown eyes throughout the episode, but when his eyes bulge out of his head, they are blue in color.