Trolls

Trolls are humanoid creatures that mostly live underground and work as miners. They are blinded by the sunlight and thus are very careful to stay out of it.

Mainstream Smurfs Media
The Smurfs encountered trolls in the episode "Now You Smurf 'Em, Now You Don't" when one of them put a crystal ball outside his cave for the Smurfs to find. The crystal ball allowed the Smurfs to see their fondest dreams in it; however, when it is touched, it transports the Smurfs to the cave where the trolls instantly put them to work as slaves. A bigger crystal ball within the cave allows the trolls to watch the Smurfs through the crystal ball that they possess. When the Smurfs eventually found out the truth about the crystal ball, Papa Smurf had used the second one Handy had found to blind the trolls by sending sunlight through the ball into the cave, allowing him and some of his remaining little Smurfs to free the captives.

In "Brainy's Smarty Party", Papa Smurf relates to the Smurflings how one time he wanted to attend an old troll's party but was not allowed to do so because he was not an old troll, though eventually he learned how to have fun with his friends in other ways.

In the 2011 Smurfs movie, the Smurfs mistake a person in an Elmo walk-around costume in New York City for a red troll.