Everything is back to what is used to be but, Olaf who has left her heart is aching. But, Elsa suddenly asks Anna "Do you want to make a snowman with me?". What is does this question mean? Yes, we can't left him. Olaf is born again by Elsa's magic and everyone's are delirious with joy. They thought  think everything has ended with a happy ending, but Kristoff says "Their There is one thing left." That is to propose to Anna.