Playing golf with clients is one way to 'mix business with pleasure'. [=to do something enjoyable that is related to your work]
I accidentally 'mixed up' the two files. [=I put each of the files in the place where the other one should have gone]
He 'got mixed up in' a plan to destroy the government. [=he became involved in a plan to destroy the government]
(..) No, thank you. You made the right call. Cheerleaders are a very subversive group. You don't wanna mix with that crowd. No, thanks. I used to be one of them. Oh, so you know. I do. Um, were you? You weren't a (..)2009 TvShow: Heroes Title: Chapter One 'Orientation/Jump, Push, Fall' Season: 4 Episode 1