'The Gift' is a prequel to this film...

If you've seen both, think about it:

Jason Bateman's character is recently (presumably) divorced at the end of "The Gift", and also out of a job. With that, the same guy offering handjobs in the bar (Horrible Bosses) is also an employee up for the same job in "The Gift", whom Simon (Jason Bateman) gets fired.

Even better, the lead detective investigating the case in The Gift is also the same lead detective investigating the case in Horrible Bosses. Mind. Blown.