The subtlety of Swanberg's films is always notable, but Happy Christmas is slightly too uneven to be his best work. Swanberg is famous in indie circles for his semi-improvisational, ultra-realistic mumblecore indie dramas, with his last film before this one, Drinking Buddies, being his most commercially successful. His style can lead to uneven results. While some actors are up to the task of taking the concept of their roles and running with them, others seem stifled rather than empowered by the unscripted portrayals. Kendrick, who was good in Drinking Buddies, seems unable to fully capture what Jenny is about, whereas Swanberg and Lena Dunham, who plays Jenny's old friend, Carson, know exactly how to add layers of humor and depth while still keeping it real.
Probably the biggest scene-stealer of all is Swanberg's baby, Jude, already a veteran "actor" who has appeared in both of his parents' projects (mom is Kris Swanberg, who makes a brief appearance here as the landlord of a messy house share that Jenny visits). Baby Jude's attempts to talk and kiss and cuddle his dad and other characters are ridiculously genuine and sweet, and they make Joe and Kelly, the new parents trying to figure out how to balance their parental obligations with their professional aspirations, much more compelling than Jenny, who's a lot less self aware than the striving Girls characters Dunham created.