Kramer vs. Kramer may not be a flashy title, but it packs a big, meaningful punch. For starters, it's a reference to the film's climactic court case. Kramer vs. Kramer is how Ted and Joanna's custody case would formally be filed, just like Marbury v Madison or Brown v Board of Education.

Speaking of punches, it's also a nod to how boxing matches and UFC fights are billed, like Frazier vs. Ali or Griffin vs. Bonnar. Ted and Joanna slug it out (metaphorically, of course) over who should be Billy's primary caregiver and what the roles of mothers and father should be.

Finally, it acknowledges the inner conflict that Ted and Joanna both experience. Ted has to learn how to be a full-time dad when he also wants to be climbing the corporate ladder. At the same time, Joanna's so conflicted about her socially prescribed roles as a wife, mother, and modern woman that she has to skip town to figure it all out and restore her mental health after years of neglect by Ted. In this way, the film doesn't just set up Ted vs. Joanna; it also pits Ted against Ted and Joanna against Joanna.