Michel looks as if butter wouldn't melt in his mouth, but don't be taken in by him.

（マイケルはいい人ぶってるけど、だまされちゃダメよ。）
　英会話レッスンで配られたプリント「食べ物にまつわる表現特集」にあった表現。

• "butter wouldn't melt in someone's mouth" = "look very innocent (but is not really)"。「バターが口でとけない人」っていうのが「悪意のない人」を表しているのがとても面白いなと思った。内がメラメラしてないから腹に一物持ってない→悪意がない、といった発想か？「虫も殺さぬ顔をして」という表現が訳であてられていることが多い（が、日常会話であまり使わないのでここでは敢えて当てなかった）。
  • She looks as though butter wouldn't melt in her mouth but I've seen her fighting with the younger kids.
• be taken inは「だまされる」という意味。
  • Don't be taken in by products claiming to help you lose weight in a week.
  • I was taken in by a fraud.
  • Not only have you been taken in by a totally idiotic rumor, you have been taken in by a totally idiotic rumor that is years out of date.