Francis' fighting style utilizes wing chun and capoeira.
When Francis enters the ballroom and notices it's set up for a wedding, you can see a banner at one end of the room that reads, "Congratulations Phoebe & Mike" - another reference to "American Ultra" (the main characters).
The tune Francis whistles throughout the movie is the same tune Hawkeye Pierce from M*A*S*H whistles
Sam Rockwell (Francis) is 16 years older than costar Anna Kendrick (Martha).