I can summarize for clarity's sake. "The Empire Strikes Back" was a film with energy that starts high, gets higher, and leads Luke into crippling failure to set-up the next film. Rey's rise is meteoric and that is good because we need to be surprised but it would have been more interesting if she over-shot the mark and, for example, compromised the hull of a spaceship while she calibrated her powers (*wink*). "The Last Jedi" is enjoyable, and I will see the next film, but the writers/directors missed opportunities with Rey.
Olaf is 'fully character' and 'fully symbol' from the moment that Anna, Christoph, and Sven hear his voice. Elsa's dormant playfulness is awake -- and much more. The preceding animation features panoramic, crystalline winter beauty -- frozen waterfalls, glitter encrusted willows -- causing Anna to declare "I never knew that winter could be so beautiful." Olaf enters with vivid color suggestions; his antics are rife with comic relief, gags only a snowman could complete, and his song about summer seems to be part of the fun. "I don't know why," says Olaf, "but I've always loved the idea of SUMMER and SUN and all things HOT--" Theatrical improvisers relish 'games' like this one: his character- deal is to obtain something fatal to only him! We're treated to some quality comedy as Olaf's solo absorbs us into a jump-cut-montage of warm environs where snowmen would perish; hilarious! Though it would be an excellent throwaway sequence, Olaf's role in the rest of the movie leads me to believe that his summer-time aspirations are thematically key.
The person who snatches the glove rarely understands what is beneath. Anna releases the literal winter within Elsa in a heated moment. Elsa takes that unwanted first step into the unknown, toward finding-out what she's capable of doing-- forced to embrace the risk of loss. I never wanted that moment, either. I know what it feels like to be a storm pretending to be a statue; to try to hold 'the stage'; to believe that life depends upon a glove. She loses control. They call her a monster. She flees. Her fears come true and even worse. Feel that with me.
Like many of us, Anna thought she could break her lonesome "spell" with a romance, unaware of the antecedent spell in her family. Elsa was correct: "You can't marry a man you just met." Yet I want to defend Anna's initiative: she was outside the gate. Hans didn't come 'calling', she found him while in town, exploring. Unfairly, their parents died unexpectedly and Elsa's reticence took away opportunities for sisterly mentoring. Anna committed a mistake but at least she wasn't paralyzed. Throughout the entire film, Anna takes action: she is on the heroine arc! Anna is the one who seizes Elsa's glove, precipitating the advent of Elsa's full power and an instant winter. The results are terrible, terrifying, and ultimately terrific (see that?). Falling for Hans is part of Anna's heroine arc and key to plot development-- heroines commit blunders, whereas inert princesses are perfect... ly helpless. Anna is our beloved heroine because she is one of us blunderers!