Star goes out into the field to understand why Mewmans treat Monsters unfairly.
While out shopping in the market, Star notices that a monster gets kicked out by a Mewman simply for trying to shop there. The Mewman attempts to do the same to Tom, but upon realizing who he is, apologizes profusely. Star approaches Moon about this; asking what makes people like Pony Head, Lekmet, Rhombulus, Rich Pigeon and Tom different from all the other monsters that inhabit Mewni. Moon gives different answers from being friends for years, importance and even just the families being rich. Star is bothered by this dilemma and demands to know who came up with the supposed rules for this. Moon reveals that Dr. Jelly Goodwell is the one who does the research on monsters and the one who decided most of these things. In a huff, Star decides to approach her directly for some answers.
After going through numerous wrong rooms, Star finally meets Dr. Goodwell, a elderly eccentric, and possibly senile, woman. Star announces her frustrations on Mewman and monster relations and Dr. Goodwell surprisingly agrees; feeling that monsters do not get enough respect. She takes Star "into the field" to study monsters up close. They trek into the forest where they end up at Dr. Goodwell's tree house lab and look out at a well established monster village where Buff Frog and his tadpoles live. Dr. Goodwell has never actually directly interacted because she believes bad things will happen if she does. She resolves to cut off the top of a local dam, which she mistakes for a monument, so that the water can flow out around the monster village and cut them off from the rest of Mewni.
Dr. Goodwell activates the explosion and Star is angered and runs to warn Buff Frog. He is unfazed, but when Dr. Goodwell accidentally shakes his hand with the detonator, it destroys the whole dam. All the monsters and Star band together to create a new dam with Dr. Goodwell redeeming herself by helping. They all succeed and Dr. Goodwell changes her philosophy. Instead of separating Mewmans from monsters, Mewmans should act like them, and then proceeds to get dirty. Star decides to hire Buff Frog as Mewni's new monster expert.
- Eden Sher as Star Butterfly
- Grey DeLisle as Moon Butterfly
- Rider Strong as Tom Lucitor
- Carol Kane as Dr. Jelly Goodwell
- Fred Tatasciore as Buff Frog
- Kimaya Thais as Katrina
- Queen Butterfly continues preparing for Eclipsa's trial.
- It is revealed that the Butterfly Kingdom appoints a monster expert to determine which creatures are deemed as monsters and which are not.
- Ludo's monsters make a brief reappearance
- Dr. Jelly Goodwell is similar in name and profession to British primatologist Jane Goodall, who studied Chimpanzees.
- The Dam of Constant Sorrow is named similarly to the 1913 folk song "Man of Constant Sorrow".