Here's a premise for you: Jason Bateman, Jason Sudeikis, and Charlie Day (of It's Always Sunny in Philadelphia fame) are buddies.
Done. Movie greenlit.
This is probably NOT how the pitch for Horrible Bosses actually went down, but after seeing the film, I don't think it's actual premise was as critical to its success as was the chemistry and loveability of its leading men. These funny guys are funnier together. Of course, Horrible Bosses is also about bosses. Kevin Spacey plays Jason Bateman's megalomaniacal coroporate boss, stringing him along with a promise of a promotion that never seems to come. Jennifer Aniston is Charlie Day's sexy-but-psychotic boss, a dentist who doesn't understand the concept of "sexual harassment in the workplace." And Colin Farrell plays the coked-up, douchey new head of Jason Sudeikis' small business. Each of these actors revels in his or her exaggerated character, each a delicious foil to the normal-guy lead they boss around. Top it off with a cameo by Jamie Foxx as a shady ex-con with a dubious grasp on the murder business, and you've got a movie that's worth seeing for the cast alone.
After a relatively slow set up that solidifies the horribleness of the main characters' respective bosses, the movie takes off with a consistently hilarious stream of antics. Bateman, Sudekis, and Day play distinct good-guys-gone-bad, each with his own personality and quirks. It's hard not to root for them, whether they're hell-bent on murdering one of their buddies' bosses or totally chickening out on a count of their inner humanity. It's kind of like The Hangover, except the guys are sweeter, and the havoc they're wreaking is NOT fueled by mind-altering drugs or alcohol. For the most part.
That's the genius at the heart of this essentially silly movie: cast normal dudes we can root for, so that when they do bad things, we're quicker to relate to their plight ("Yeah, I'd kill him too, if he were my boss!") than to judge them ("How could he stoop so low!"). Excellent work, casting directors. Now get to work on casting villains for the less-funny, zanier sequel!
