This phrase is not new; the full phrase is "to take the
Mickey (out of someone)"
Britons have been using this figure of speech for decades, if not centuries. A "Mickey" of course, is a "Mick": a pejorative, racist term for an Irishman (so nicknamed because so many
Irish surnames begin with Mc- or
Mac-) It is a common stereotype, in both the UK and USA, that
Irish men have volatile tempers, like to brawl, and make good boxers. So, To "take the Mickey (out of someone)" means to take the fight, the vigor, the gravity, the self-importance out of them, by mocking them, usually in a very subtle
way.
Headmaster: "...so I expect you boys to comport yourself with the full dignity befitting students of this establishment of secondary learning."
Student: "Oh yes, we will sir. We'll
even wear our school blazers to bed."
Headmaster: "If I didn't know
better, I'd think you were trying to take the
Mickey out of me!"