butter wouldn't melt

butter wouldn't melt (in (one's) mouth)

Said of one who appears innocent or reserved in certain company, when in fact one may have the opposite demeanor. Sure, he looks as if butter wouldn't melt in his mouth when he's around people he doesn't know, but stay a while and you'll see what he's really like.
See also: butter, melt

butter wouldn't melt (in someone's mouth)

Prov. Someone is acting as if innocent. By the time her parents came home, Emily had cleaned up all evidence of having broken the valuable figurine, and she looked as though butter wouldn't melt in her mouth. Jane: How can you suspect George of playing that practical joke on you? He looks so innocent. Jill: Yes, butter wouldn't melt, I'm sure.
See also: butter, melt

ˌbutter wouldn’t ˈmelt (in somebody’s ˈmouth)

(spoken) a person looks very innocent, but probably is not: She looks as if butter wouldn’t melt in her mouth, but don’t be fooled by first impressions!
See also: butter, melt
References in classic literature ?
There's old Stephen Grant coming in," exclaimed Peg viciously, shaking her floury fist at him, "and looking as if butter wouldn't melt in his mouth.
Jock' Horner they call him, so quiet-like an' easy-goin', soft-spoken as a girl, till ye'd think butter wouldn't melt in the mouth iv him.
These mean, soft chaps, that you would think butter wouldn't melt in their mouths, were the ones to make a wom- an thoroughly miserable.
Then he throws in a quick butter wouldn't melt expression and all is forgiven, obv.
I was on an early morning flight a few months back when a woman who looked as if butter wouldn't melt in her mouth suddenly declared to all and sundry it was party time - at seven in the morning.
I have a gentle male friend who looks like butter wouldn't melt in his handsome mouth.
Holly Comber-Moccia provides the perfect foil as Christine Colgate, the butter wouldn't melt in the mouth 'little innocent' American heiress, who becomes the target for the conniving duo.
Taylor Swift The singer looks like butter wouldn't melt in this angelic frock, as she pairs a lace dress with her signature red lippy and nude accessories.
All right, so she's fallen out with KATHERINE JENKINS and ALED JONES, but she sang like butter wouldn't melt at the Jazz Pizza Express in London's Soho on Wednesday.
She may be adorable and look like butter wouldn't melt in her mouth but greyhound Jasmine sparked a full-blown gas scare at a housing estate.
Andrew Castle - like the politically correct, butter wouldn't melt in his mouth wimp that he is - said: "I know he's upset but I must apologise for the language.
FRIDAY Don't let the butter wouldn't melt look fool you, Simon Amstell combines vulnerability with razor sharp wit and a talent for provocation.
Another parent added: "She was so prim and proper, the sort where butter wouldn't melt, she came to visit me at home when I first enrolled my child for school.
TO look at Sarah Millican you would think butter wouldn't melt in her mouth.
I've said it before Vicar," she began, looking for all the world like butter wouldn't melt in her mouth.