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 theMickey (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 theMickey out of me!”