In one scene, Robert De Niro's character is confused as to who Jay-Z is. This is an in-joke about the beef Robert De Niro and Jay-Z had between 2012 and 2016.
In the scene where Jules goes to get Ben from the coffee shop, the names "Annie" and "Hallie" are seen on two of the cups. Those are the names of the twins in the 1998 version of The Parent Trap (1998), which is also directed by Nancy Meyers. Annie and Hallie are also the names of Nancy Meyers' daughters.
When Ben tells Jules that he knows a faster way to get to the office, he mentions that he used to drive a cab. DeNiro's breakout character Travis Bickle was a cab driver.
Writer and director Nancy Meyers approached Jack Nicholson for the role of Ben Whittaker. Nicholson is mentioned in Jules' philosophic rambling at the bar.