Almost nothing about Office Christmas Party could be described as "subtle," but there's one low-key moment that will make pop culture fans squeal with excitement. Jennifer Aniston's character is at the airport waiting for her flight, and you can catch a quick glimpse at the book she's reading: The Girl on the Train by Paula Hawkins. The very same book that was adapted for the big screen this year, starring guess who? Aniston's husband, Justin Theroux. Boom! We see you, Aniston.