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]
(..) There's no guarantee that our sperm is going to generate high-iq offspring. Think about that. I have a sister with the same basic dna mix who hostesses at fuddruckers. Sheldon,this was your idea. A little extra money to get fractional t- bandwith in the apartment. I know, and I do yearn (..)2007 TvShow: The Big Bang Theory Title: Pilot Season: 1 Episode 1