Sofia, James and Amber are flying kites when Sofia trips and loses hers. She is about to go down and retrieve it when Amber tells her the area down below is where the Castle Trolls live, and that they're supposed to be dangerous. However, Sofia still goes down there, anyway, though she is scared off when she sees a troll peering out through the rocks and leaves her torn kite behind. Sofia brings up the trolls at dinner, which prompts King Roland to mention the story of King Gideon and the trolls. Back when their great-grandfather Gideon was King, he heard a loud thumping outside the castle one night, and discovered a bunch of trolls banging their clubs on the ground. The frightened King summoned his guards to chase trolls away and since then no one has ever seen them outside their cave because King Gideon later made a rule saying that the trolls have to stay below in their cave and the castle's inhabitants have to stay above close to the castle.
The next morning, Sofia's repaired kite has somehow been returned to her. Realizing the troll she saw yesterday fixed it and returned it, she decides to go and thank him. While Sofia is looking around in the cave for the troll, he pulls her off the bridge she was crossing, since it's unsafe. He then introduces himself as Gnarly and brings her to the grotto, where there is a giant wall of crystals that look like a starry night sky, since the trolls love looking at stars. When Sofia asks why they stay in the cave looking at these fake stars instead of going out to see the real ones, Gnarly tells her the story she was told last night, though from the trolls' point of view: Their great-grandparents went out to look at the stars and were so happy they started banging their clubs on the ground, before they were chased away by the king's guards and forbidden to leave their cave again. Sofia also learns that the trolls make music by banging their clubs against the ground, and realizes that King Gideon's story was all a misunderstanding that occurred because the late King had jumped to conclusions without getting the facts first. Sofia tells James about her meeting with the trolls and what actually happened between them and King Gideon. The two decide to come up with a plan to show everyone there is no reason to be afraid of the trolls. When they notice a troupe of acrobats going into the castle, who will be performing for their family that night after dinner, Sofia comes up with an idea to have the trolls perform for the King and Queen. Sofia tells Gnarly that she and James can sneak them in while everyone else is having dessert, and they will hide until the acrobats are finished. Although Gnarly is unsure, he still chooses to go along with the plan.
After dinner, Sofia and James claim they are full and don't want dessert and then run off. The trolls are successfully brought into the throne room and hidden behind the curtains, where they will wait until Sofia announces there is one more surprise. Once the acrobats are finished, Sofia makes the announcement and, after James pulls back the curtains, the trolls reveal themselves and begin to make their music. Thinking they're attacking, Roland orders his guards to seize them despite Sofia's plea to leave them alone. The trolls manage to escape, but Roland remains displeased about Sofia bringing them into the castle and has her along with James and Amber sent to their rooms until the castle is safe, as he plans to have a guard placed outside the trolls' cave by tomorrow. Knowing she may never see her new friends again, Sofia goes to the cave with her animal friends so she can apologize to Gnarly and say goodbye since this will be her only chance to do so. In her haste to get to the cave, Sofia fails to notice that she has been spotted by Roland who goes after her. Roland manages to catch up with Sofia as she once again crosses the unsafe bridge resulting in the two of them falling through it and into a pit. Trapped together at the bottom of the pit, Sofia manages to get her father to see that everything that everyone believed about the trolls was wrong and the whole "troll attack" was a huge misunderstanding that happened because his grandfather jumped to conclusions without even trying to get the facts first just like he did. Just then, Gnarly and the other trolls arrive to help pull Sofia and Roland safely out of the pit. Roland apologizes for how the trolls have been treated and later goes on to issue a proclamation that the trolls are free to come to the castle and look at the stars whenever they want and Miranda makes Sofia promise she'll never go into a dark cave alone again.
- Ariel Winter as Sofia
- Sara Ramirez as Queen Miranda
- Wayne Brady as Clover
- Tim Gunn as Baileywick
- Darcy Rose Byrnes as Princess Amber
- Zach Callison as Prince James
- Travis Willingham as King Roland II
- Ashley Eckstein as Mia
- Meghan Strange as Robin
- Zoe Robb as Teeni
- Carlos Alazraqui as Gnarly
- The title is based on "Let the Good Times Roll".
- "Let the Good Times Roll" is also the name of a jump blues song by Louis Jordan.
- This episode also makes references to two songs by Qulinez, "Troll" and "Noise".
- This is the first time Roland shows that he is very protective of Sofia.
- This is the first time Sofia is seen wearing a robe.
- This is the first time Sofia strengthens ties between her family and supernatural creatures.
- Moral: Don't jump to conclusions until you have all the facts.