le jupon dépasse

Etymology
lit. 'one's slip (underskirt) is showing'.

Phrase

 * 1)  one's hidden intentions or an embarrassing truth have been inadvertently exposed; one is showing one's true colours.
 * 2) * 2006, Canada. Parliament. House of Commons, House of Commons Debates, October 3, 2005 (Hon. Pierre Pettigrew):