Trolls are short, green, and furry creatures found in the Kingdom of Enchancia. They only come out at night because the sun's too bright for their eyes, but starlight is just right. For this reason they love to come out and look up at the stars, and when they're happy, the bang their Troll Clubs, which is how they make their music.
Unfortunately, one night they did this in the castle courtyard where they were seen by King Gideon. Gideon thought the trolls were attacking the castle and had his guards chase the trolls into their cave beneath the castle, whereupon he forbade them from ever leaving their cave.
The trolls put up sparkling stones on the roof of their caves to mimic the nightsky full of stars, but they were still sad because it wasn't the same as the real thing.
One day, many years later, when King Gideon's grandson Roland II was king, a troll named Gnarlie met Princess Sofia, the new stepdaughter of the king, to whom they reveal what really happened, and despite a rough start, with her help they show everyone else they're not monsters, and are allowed to come out at night to look up at the stars again. Some trolls are voiced (uncredited) by Tara Strong and Carlos Alazraqui.