It starts at the Krusty Krab when SpongeBob realizes they're out of tartar sauce, but when he checks the vat, he realizes it's empty and it has been there for 50 years. When Mr. Krabs yells at him to get back to work, SpongeBob explains the situation. Mr. Krabs gets an idea to start a time capsule.
The next scene shows the tartar sauce vat next to a hole with a large stage next to it. A huge line of people are in line to make contributions and Mr. Krabs tells SpongeBob and Squidward to handle them while he sells souvenirs. It shows several people making contributions which Squidward critiques but SpongeBob finds everything amazing. Mr. Krabs sells cheap souvenirs for outrageous prices. Patrick comes to make a donation of his favorite rock. Squidward lets him put the rock in the air but hits the wood behind him, flinging Squidward, SpongeBob, and Patrick into the Time Capsule, trapping them. Mr. Krabs puts a copy of the Krabby Patty formula in the capsule, making Plankton interested.
In the time capsule, the 3 of them imagine what the future would be like until Squidward gets knocked out. Plankton drills into the capsule, hitting shaving cream that sprays Patrick which gives him a beard and Patrick sprays SpongeBob and Squidward. Squidward wakes up, thinking it's been 50 years due to the beard and escapes through the hole Plankton created. The "future" isn't what Squidward wanted, so he goes back to the time capsule shoving the formula into Plankton's mouth on his way back. The episode ends with Plankton constipated with his body shaped like a bottle and Karen calls him "poopsy" and Plankton asks for more prunes.
The time capsule date had the year of 1960 on it and this episode aired in 2010. In real life, 2010 actually is 50 years after 1960. At the beginning, when SpongeBob sees the date on the time capsule (May 1960), he infers that it has been there for 50 years.
Since the bottle would have passed through his system by now, Plankton should now have the formula. However, it is unknown if or how he lost the formula. It could have smashed in the toilet and ruined it, or accidentally got flushed. Another possibility would be that Mr. Krabs, suspecting that Plankton might be watching, had left a decoy formula for him in plain sight.
There is a painting of Squidward in the Time Capsule even though everybody hates his art, he could have thrown it in there himself.
SpongeBob, Patrick, and Squidward would have all suffocated in the time capsule within a few days, and not 50 years.
Since Mr. Krabs buried the time capsule in 2010, someone will have to re-open the time capsule in 2060, which is 50 years after 2010.
When Mr. Krabs threw the formula in the capsule, the capsule was full to the brim. But when the scene cuts back to SpongeBob and company, it was barely full and seemed to be a lot wider.
Within all the chrome in SpongeBob's future thoughts, it is similar to "SB-129," although it takes 2,000 years after the main event. But "SpongeHenge" contradicts to "SB-129" as well, as 3,000 years after the main event, there is no chrome background.
When SpongeBob and Patrick are playing Pretzel Pals, Patrick said "forehead on yellow" when he was actually using the back of his head.
When Squidward is touching his "beard" it doesn't make sense that he wouldn't notice it is not hair and doesn't come off on his hands.
In Indonesia, when Squidward says "there's no way I'm letting you put your dumb rock in the time capsule." and "We just got buried alive, you idiots!," the word "dumb" and "idiots" is muted because the words "dumb," "idiot," "moron" and "stupid" is considered profanity in Indonesia.
This could be based on the Nickelodeon time capsule that will be opened on April 30, 2042. It was buried in 1992 at the old Nickelodeon Studios at Universal Studios in Orlando, FL. after the closure of the building and remodeling it for the Blue Man Group, it was reburied at the Nickelodeon Suites Hotel in again, Orlando, about 10 or so miles from Universal.
When SpongeBob dreams of technological future advancements, the teleporting noise is Star Trek 's famous "beaming" sound.
Pretzel Pals is a parody of the game called Twister.
When SpongeBob throws the plate, it breaks, but when they're trapped inside, the plate is back together again.
The switch on the toaster that was donated was pushed down and did not have a cord.
In the crowd outside the time capsule, there are multiple identical fish.