The head troll is a minor character on Once Upon a Time. He was the leader of the group of trolls that made a deal with Snow White, buying several stolen jewels from her. When Snow returned to the bridge under which they lived in order to revert the deal and retrieve the jewels to their rightful owner, Prince Charming, the head troll became suspicious that they were being set up and got aggressive, engaging in a fight with the prince and ultimately being transformed into a bug by Snow White.
Before the Curse
Snow tries to retrieve Charming's ring. ("Snow Falls")
Snow White and Prince Charming are riding the horse they took through the Enchanted Forest, hoping to find the trolls with Charming's jewels. They trot up to an entrance way to a bridge, it seems secluded and unfriendly, Snow dismounts her horse followed by Charming who does the same, Snow walks with the horse and makes a loud noise, spooking it, and sending it away. "Trolls don't like horses... We walk from here. Follow me, and keep quiet." she instructs him, the two of them approach the Troll Bridge. The two of them walk a small way across the bridge and Charming asks where the trolls are, Snow simply walks over to the bridge's edge, assuring him that they're here, and places a small pile of gold coins on the ledge. Three trolls soon arrive, one exclaiming that he thought they were done, referring to his deal with Snow. Snow says that she wishes to make another deal - she'll give them back their money in exchange for the ring. The trolls are still focused on Charming however, which results in a battle between Snow and Charming vs. the trolls. Snow ends up saving Charming's life by using her magic dust to turn the trolls into bugs. When leaving the bridge, Charming steps on them, killing them. ("Snow Falls")
After the Second Curse
Dead again. ("There's No Place Like Home")
With time having been altered by Emma and Hook upon falling through a portal to the Enchanted Forest of the past, the two of them try their best to get it back on track and manage to make it so Snow and Charming head to the Troll Bridge. However, with Snow already having used the dark fairy dust she used the first time on herself to escape a sticky situation, she has no weapon to defend herself with. She manages to get away, but sees that Charming is still in trouble, and so she uses sand to bluff her way out of the situation, making the trolls retreat. However, Regina discovers that the trolls let Snow slip through their fingers and so she turns them to cockroaches herself, going on to squish them dead. ("There's No Place Like Home")