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, the grandfather of King Roland II. Gideon thought the trolls were attacking the castle and had his guards chase the trolls into their caves beneath the castle, whereupon he forbade them from ever leaving their caves.
The trolls put up sparkling stones on the roof of their caves to mimic the nightsky full of stars but they were sad because it wasn't the same as the real thing.
One day a troll named Gnarlie met Princess Sofia to whom they reveal what really happened, and despite a rough start, with her help they show King Roland they're not monsters, and are allowed to come out at night to look up at the stars. Some gnomes are voiced (uncredited) by Tara Strong and Carlos Alazraqui.