The episode begins at the Simpson household during breakfast, where Marge tries to feed Maggie pancakes. Maggie refuses to eat them because Marge has not put ranch dressing on the pancakes, and Maggie only eats food with ranch dressing. After Marge gives up and adds ranch dressing, the family receives an emergency alert on their television. Kent Brockman announces that a swarm of Dutch Leaf Slurper caterpillars has invaded Springfield. Mayor Quimby declares a lockdown of the town until the caterpillar situation is resolved.

The Simpsons decide to spend time together before the lockdown fully sets in, planning to watch the show Steak, Cake or Fake? on Binge+. However, Homer accidentally logs out of the streaming account, causing the family to panic about losing their entertainment.

The next day, Springfield Elementary switches to remote learning using the ChatHippo platform. After the school day ends, Principal Skinner forgets to turn off his webcam, which allows Bart to spy on him. Skinner's cousin Peter is staying at Skinner's house during the lockdown. Peter spends his time sweet-talking Agnes Skinner and insulting Seymour Skinner.

Meanwhile, Marge tries to get Maggie to eat other dips since they have run out of ranch dressing, but Maggie refuses. Marge asks Homer to check if Ned Flanders has any ranch dressing. When Homer attempts to take some of Ned's apocalypse survival food, Ned imagines Homer stealing from him and his sons Rod and Todd. Ned then takes back the food and only gives Homer a small cup of ranch dressing.

Marge thinks they can ration the ranch dressing for a few days, but Lisa warns that the lockdown could last for months. This causes Maggie to drink the entire small cup of ranch dressing immediately.

Throughout the episode, the caterpillar invasion causes a grim atmosphere in Springfield, with Professor Frink acting as an expert from the Center for Disgusting Caterpillars. He rates the caterpillars on a scale of ickiness, emphasizing the severity of the infestation and the unpleasantness it brings to the town.

The lockdown forces the Simpson family to spend extended time together, leading to various interactions and tensions, especially with the presence of Skinner's cousin Peter, who disrupts the household dynamics.

The episode ends with the family still coping with the lockdown and the caterpillar plague, highlighting the challenges of being confined together and the scarcity of simple comforts like ranch dressing.

At the end of "The Very Hungry Caterpillars," the insect plague in Springfield is finally resolved, and the lockdown is lifted. The Simpsons family, having endured the quarantine together, come out of isolation with their relationships tested but intact. Principal Skinner recovers his family quilt with Bart's help, and Maggie's demand for ranch dressing is humorously fulfilled. The episode closes with the town returning to normal life after the crisis.

The ending unfolds as follows:

The episode culminates after a prolonged lockdown in Springfield caused by a swarm of Dutch Leaf Slurper caterpillars, which forces everyone to stay indoors. The family has been confined together, facing the strain of isolation and the challenges of the insect invasion.

Marge, after much frustration, finally gives Maggie ranch dressing to accompany her food, a small but significant moment of relief for the baby. This detail highlights the family's attempts to maintain normalcy and comfort despite the chaos outside.

Meanwhile, Bart and his classmates assist Principal Skinner in recovering a cherished family heirloom--the Skinner family quilt--which had been conned away by Skinner's Cousin Peter. Their teamwork results in Skinner regaining the quilt, symbolizing a restoration of order and personal dignity for him.

As the caterpillar threat diminishes, Kent Brockman announces that the plague is over, and Mayor Quimby lifts the lockdown restrictions. The townspeople emerge from their homes, relieved but changed by the experience. The Simpsons, having spent intense time together, show signs of having weathered the emotional and interpersonal challenges the lockdown imposed.

Each main character's fate at the end is as follows:

• Homer and Marge: They reconcile their frustrations and support each other through the lockdown, ending on a note of mutual understanding.

• Bart: He plays a key role in helping Skinner, showing growth in responsibility.

• Lisa: Though agitated during the lockdown, she adapts as the crisis resolves.

• Maggie: Her simple demand for ranch dressing is humorously fulfilled, underscoring her innocence amid the turmoil.

• Principal Skinner: Regains his family quilt, symbolizing a return to stability.

The episode closes with Springfield returning to normal life, the insect plague behind them, and the Simpsons family having endured their greatest challenge yet--being locked down together.

The Simpsons Season 34, Episode 20 titled "The Very Hungry Caterpillars" does not have a post-credit scene. Available sources, including episode summaries, IMDb's crazy credits section, and fan wikis, do not mention or describe any post-credit or after-credits scenes for this episode. The episode ends with the conclusion of the story about the Simpson family coping with a caterpillar invasion lockdown in Springfield, and the credits roll without additional scenes afterward.

Therefore, there is no post-credit scene to describe for this episode.

Principal Skinner's cousin Peter stays at Skinner's house during the lockdown and spends his time sweet-talking Agnes and insulting Seymour. Bart spies on Skinner through a webcam that Skinner accidentally leaves on after school ends.

Maggie refuses to eat pancakes unless they have ranch dressing on them. When the family runs out of ranch, Marge tries to get Maggie to try other dips, but Maggie refuses. Homer tries to get ranch from Ned Flanders, who only gives him a small cup after imagining Homer stealing food. Lisa warns the lockdown could last months, prompting Maggie to drink the entire cup of ranch dressing.

A swarm of Dutch Leaf Slurper caterpillars invades Springfield, leading Mayor Quimby to announce a lockdown until the situation is resolved.

Springfield Elementary switches to remote learning via ChatHippo. After school, Bart spies on Principal Skinner through his webcam, which Skinner accidentally leaves on.

Homer tries to take some of Ned's apocalypse survival food, but Ned imagines Homer stealing from him and his sons Rod and Todd. Ned then takes the food back and only gives Homer a small cup of ranch dressing, which is important because Maggie needs ranch to eat.

The Simpsons Season 34, Episode 20, "The Very Hungry Caterpillars," is rated TV-PG and generally family-friendly but contains some content that might be potentially objectionable or upsetting for children or sensitive viewers.

Potentially sensitive aspects include:

• Mild sexual content: A brief scene with a woman depicted naked but modestly covered by hair and a leaf.
• Moderate violence/gore: A non-graphic moment where Principal Skinner mimes shooting himself in response to a bad joke.
• Moderate profanity: Use of words such as "bitch," "hellish," "sucks," "hellfire," "screw this," and "hell."
• Mild frightening/intense scenes: The episode features a somewhat apocalyptic atmosphere due to a caterpillar invasion causing a lockdown, which might feel intense or unsettling, especially as it parodies pandemic lockdowns.

There is no depiction of alcohol, drugs, or smoking in this episode. Overall, while suitable for older children and adults, parents of younger or sensitive children might want to be aware of these elements before viewing.