As stated in the DVD audio commentary, the bar where Stephen meets Tom Duffy is called Head First and is located directly across from the Cincinnati Reds baseball stadium. It's named for Pete Rose, who would slide head first. Paul Giamatti, who plays Tom Duffy, is the son of the late Bart Giamatti, who as Commissioner of baseball imposed the lifetime ban on Pete Rose.
The Ides of March was the day (March 15) that Julius Caesar was assassinated. In Shakespeare's "Julius Caesar" before being stabbed to death, Caesar is told by a Soothsayer: "Beware the ides of March."
After watching Morris stating on a video that extremism cannot be faced with more extremism and that America should understand why its enemies behave as such, Ryan Gosling's character mockingly says "Hello, my name is Neville Chamberlain and I'd like to be your Commander-in-chief". This is a reference to the attitude of the British Prime Minister who, before World War II, blindly believed he could negotiate with Hitler towards peace, with disastrous consequences.
At the church funeral for Molly Stearns, whose family is portrayed as being devout Catholics, her casket is parallel with the altar and it is not covered with a pall.
A funeral in a Catholic church for non-clergy would have the casket positioned so that the feet would enter first and the casket would remain feet end pointing towards the altar (i.e. the deceased would be facing the altar), and the casket would be covered with a pall - a type of cloth that covers the casket.
Ryan Gosling's character is shown shaving in the bathroom as he gets ready to go somewhere, in the next scene, supposedly right after he's shaved, he's back looking like he has at least 1-2 days of beard growth (which is the character's usual look).
When Paul is sitting in the barber shop getting a haircut, the barber goes over the same spot on the back of Paul's neck. After 6 times, there are no hair clippings and the hair is no shorter.
Tom Duffy: Do yourself a favor. Get out, now. While you still can. Go into entertainment or business, go open a fucking restaurant in Costa Rica. Anything. Do something that's gonna make you happy, okay? Cause you stay in this business long enough, you're going to get jaded and cynical.
On a couple of occasions Ryan Gosling's character asks his interns if they are "Bearcats" - what does this mean?
A
It's another way of asking if they went to the University of Cincinnati where the 'Bearcat' is mascot. (Towards the end of the film, when a new intern came in and she was asked that question, if she was a "Bearcat," she replied no, that she was a "Buckeye" which is the term used for those from Ohio State University 'Buckeyes').