The road to bromance isn't always paved with emotional talks about each dude's innermost thoughts and feelings or excessively long garage-band jams, as illustrated in the bromance to end all bromances between Peter Klaven (Paul Rudd) and Sydney Fife (Jason Segel) in 'I Love You Man.'

Sometimes, potential bros can't stand each other at first, as in this week's release 'Due Date' starring Robert Downey Jr. as a father-to-be forced to hitch a ride with an annoying aspiring actor, played by Zach Galifianakis. But this rocky beginning doesn't necessarily mean the two men can't eventually develop a beautiful friendship, much like the original cinematic bromance between Rick Blaine (Humphrey Bogart) and Captain Louis Renault (Claude Rains) in 'Casablanca.' Even though Rick double-crossed Renault, the movie ends with the two men sauntering off into the fog, with Rick proclaiming, "Louis, I think this is the beginning of a beautiful friendship.'

There have been so many beautiful friendships among movie bros since 'Casablanca,' it can be a bit difficult to keep track of them all. It's even starting to look like the bromance genre has unwittingly generated a number of subgenres, including (but not limited to): Bros who hate each other at first but grow on each other (see list below); lifelong bros whose friendship is tested but emerges stronger than ever ('Superbad,' 'Stand By Me'); bros who go on a man-cation together and reinforce their bond, even if that wasn't the original intention ('Hot Tub Time Machine,' 'Swingers'); and bros who have just met and develop their bond over the course of the movie ('I Love You, Man,' 'Funny People').
categories Columns, The Rundown