In the opening scene, Jess and the gang are dressed for Halloween as the cast of The People v O.J. Simpson: American Crime Story. Schmidt is John Travolta/Robert Shapiro, Nick is David Schwimmer/Robert Kardashian, Winston is Sterling K. Brown/Christopher Darden, Cece is Kenneth Choi/Judge Lance Ito and Jess is Sarah Paulson/Marcia Clark.
When Jess and Robbie are trying to figure out a new gift for Nick, Robbie suggests tap shoes. This is a reference to the fourth season opener, where Nick mentions having bought shoes due to their being shiny, only for them to have turned out to actually be tap shoes.
When Reagan enters, she comments on how hard it was to put on her Santa outfit and Schmidt indicates that he understands. This is because, in an earlier Christmas episode, Schmidt had to dress as "Sexy Santa" for his office party.
The many elves at the bar may be a reference to the film 'Elf' in which Zooey Deschanel starred.