Warm hugs
Olaf first appears as the snowman Elsa and Anna built as kids. Years later, during "Let It Go," Elsa recreates him without noticing and he comes to life. In the woods he meets Anna, Kristoff and Sven, introduces himself, gets a carrot for a nose and sings "In Summer," dreaming of the heat.
He leads the group to the ice palace. Later he finds Anna alone in the castle, abandoned by Hans, lights a fire for her and explains what love is: putting someone else's needs before yours. In the end, Elsa gives him a personal snow flurry so he won't melt in summer.