In the 2013 animated film "Frozen," the trolls can transform into rocks.
The rock trolls live in the Valley of Living Rock, where they appear at first to be ordinary stones scattered across the landscape. When Kristoff brings Anna and Sven to them, the rocks roll and spring to life, revealing the troll community. Their leader, Grand Pabbie, uses magic to remove the shard of ice from Anna’s head and explains the danger affecting her.
The trolls’ rock form connects them to Scandinavian folklore, where trolls are often associated with mountains, boulders, and the danger of being turned to stone. In Frozen, however, the transformation is presented as a natural magical ability rather than a punishment. They can move around as rocks and then reveal their troll bodies when interacting with visitors.
A common mix-up is confusing these characters with the trolls from DreamWorks’ Trolls franchise, who do not transform into rocks. The Frozen trolls are also distinct from Olaf, who is a magically animated snowman created by Elsa. The sequel Frozen II continues to identify them as rock trolls.