a Jekyll and Hyde

a Jekyll and Hyde

someone whose personality has two different parts, one very nice and the other very unpleasant
Usage notes: This phrase comes from the main character in the book The Strange Case of Dr Jekyll and Mr Hyde by Robert Louis Stevenson.
You can't depend on him to be friendly - he's a Jekyll and Hyde.
See also: and, Hyde, Jekyll
References in periodicals archive ?
It was a game of two halves, a Jekyll and Hyde performance.
Funke would refer to him as a Jekyll and Hyde because of his sudden outbursts.
At least once a week, usually more often, a patient in my clinic describes himself to me as a Jekyll and Hyde.
The transformative effect, however, is not purely pharmacological: for many a Jekyll and Hyde has told me that a quantity of alcohol taken as beer does not have the terrible consequences for his character as the same quantity taken as whisky.
I've heard "He's a Jekyll and Hyde character" as often as I've heard "I'm a Jekyll and Hyde character.
As for the person who claims that her lover is a Jekyll and Hyde, the metaphor serves to preserve and justify her love for him, despite all the evidence that he is unworthy of it.
Having a split personality, schizophrenia, is not a splitting of the personality into multiple parts, not a Jekyll and Hyde phenomenon, despite the popular hold of the Robert Louis Stevenson story.
A woman accused of killing her taxi driver husband told police he could be like a Jekyll and Hyde character after he had been drinking.