The play received 'mixed' reviews. = The play's reviews were 'mixed'. [=some critics liked the play, while other critics did not]
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]
(..) Her name's Agnes. We're just waiting for her father. Look. I don't know how this happened. I'm so sorry. They must've gotten mixed up somehow. Tom gave us the slip. He left with the baby. Something's going on. I think they lost him. What makes you say that? (..)2016 TvShow: The Blacklist Title: Alexander Kirk (No. 14): Conclusion Season: 3 Episode 23