Take the Mickey
Tease or make fun of.
There are various forms of this: take/extract the Mick/Mickey/Michael, although the 'take the Mickey' version is most often used in print.
It is sometimes reported that the phrase originates as a variant of the slang phrase 'take the piss' and the the 'Mickey' refers to micturate. This seems rather fanciful and there's no evidence to support that view. It is now more generally accepted that the phrase came about as rhyming slang. 'Taking the piss' does play its part as the rhyming slang refers to a (yet to be identified) character called Mickey Bliss. So, 'taking the piss' became 'taking the Mickey Bliss' and then just 'taking the Mickey'. An early citation of the longer form 'taking the Mickey Bliss' would be useful here, but I've not come across one.
Who or what was Mickey?
Taking the piss is reported as originating in the UK in the 1930s and 'taking the Mickey' probably came not long afterwards. The first form of the phrase in print - as 'take the mike' - comes from 1935, in George Ingram's Cockney Cavalcade:
"He wouldn't let Pancake 'take the mike' out of him."
The precise wording - 'take the Mickey' doesn't appear in print until a few years later. The earliest I've found as yet is in J. Henry's Who lie in Gaol, 1952:
"She's a terror. I expect she'll try and take the mickey out of you all right. Don't you stand for nothin'."