Hitagi Crab (Spoilers below)

Hitagi Crab is one of the best two-episode arcs in anime that utilizes very creative, evocative visual direction to effectively illustrate Senjou's lingering trauma while also perfectly introducing the core theme of Bakemonogatari: "Only you can save yourself."

Senjougahara is initially introduced as an incredibly violent, abrasive person who keeps her guard up both physically and verbally. As the night progresses, we see her lash out to try to cover up her fears and insecurities while subtly reaching out to Araragi for reassurance.

While it's not apparent why until later on, Senjou views her body as a commodity she can use to show "appreciation" to Araragi for his help while also testing his motives.

He gives a lackluster answer to an impossible question and she lashes out to cover up her disappointment.

Senjougahara then reveals most painful memory of her life and the mystery behind her extreme behavior finally clicks into place as she reveals her mother facilitated her attempted rape that lead to the dissolution of her family.

While her mother's betrayal and the sexual assault left her traumatized, the most tragic revelation is that Seunjou thought that if she allowed her assault then she could've prevented her family from splitting up. This is the "weight" that she couldn't carry on her own.

Ultimately, the only way Senjou could save herself was by accepting the "weight" of those feeling, thoughts, and memories she had of her mother, both good and bad alike.

And that's how Monogatari introduced one of my favorite characters in just two episodes.