“Oh, I don't know why, but I've always loved the idea of summer, and sun, and all things warm...”
Olaf the Snowman (simply known as Olaf) is one of the primary characters in Disney's 2013 animated feature film Frozen. He is voiced by Josh Gad.
Official Disney Bio
He's Olaf and he likes warm hugs. Sprung from Elsa's magical powers, Olaf is by far the friendliest snowman to walk the mountains above Arendelle. His innocence, outgoing personality and uncanny ability to disassemble himself at good and not-so-good times lead to some awkward, albeit laughable moments. He may also have the world's most impossible dream, but what he doesn't know won't melt him—or will it?
In very early versions of the movie, Olaf was supposed to be one of the first guards of Elsa's castle when the concept of Elsa controlling a legion of menacing snowmen was still in the story (Notably, the only snowman minion to remain in the film would be Marshmallow). Chris Buck compared that version of the character to a trial run or someone's first pancake where the cook throws out the pancake when the cook finds out that it is burnt on the bottom.
In order to keep him from getting too complex, Chris Buck and Jennifer Lee wanted Olaf to have a childlike innocence. Like when a child makes a snowman for the first time where the heads are never perfect, and the body is disproportionate. That was the idea for the directors when they were thinking what kids would think of a snowman.
Josh Gad, the voice of Olaf, did plenty of improvements during the course of the recording sessions. But the directors were very careful not to have him in too many of them or risk him taking over the story. He is there to interject levity to the scenes. But they also gave him proper screen time. One of his major scenes will be when he sings his musical number "In Summer", which the songwriters Bobby and Kristen Lopez wrote specifically to fit Gad's vocal talent, as the two were fans of Gad's previous work.
Olaf had to earn his place in the film. Jennifer Lee says that he couldn't just be thrown in, that he had to have a purpose, and one of his purposes is that he is the embodiment of the love between Elsa and Anna.
Olaf's dream of experiencing summer. Added by Byzantinefire
“When Elsa flees Arendelle… she starts playing with the very magic she’s been hiding for so long. The snowman she creates comes form memories of the happy times she shared with Anna when they were young. Olaf represents that pure innocence and childhood joy.”
―Jennifer Lee, Frozen screenwriter
Olaf is goofy and naive, but extremely lovable and caring towards his friends, especially Anna and Elsa. Because he was built during their childhood, Olaf retains the childlike personaility that filled Anna and Elsa during those years, appearing to be very whimsical and playful when he returns as an enchanted snowman years later. He has an odd fascination for summer, possibly because young Elsa made him a snowman who loves warm hugs, and according to Olaf, he sometimes fantasizes about what summer would be like for a snowman, completely unaware of the tad consequences of his ambitious dream, making the poor snowman hapless. Olaf is also very giggly and tends to laugh a lot. He also has aspects of Anna when she was a child. An example is when they arrived at Kristoff's home, he said to Sven that "the sky's awake" just as Anna said to Elsa years ago.
Aside from his dominantly goofy side, Olaf is shown to have some intelligence to him, seen during his time with Anna in the library. Here, he teaches the princess what true love is, and that it's putting someone else before yourself, using Kristoff as the perfect example, finally giving Anna the true meaning of love. And after the climax, when Anna sacrifices herself for Elsa, thus breaking the icy curse, Olaf was the first to realize Anna's sacrifice was an act of true love (it didn't have to be romantic), and that act is what saved the kingdom. He is also not as oblivious as he seems, as he was quite skeptical about the Trolls at first when he thought they were just rocks, and even warns Anna to run because he cares for her and thought Kristoff was delusional.