Arriver comme un cheveu sur la soupe
[a ree vay kuh mu(n) sh(eu) veu sur la soop
to turn up at a very awkward moment, to be completely irrelevant
to arrive like a hair on soup
I have mixed feelings about the French expression arriver comme un cheveu sur la soupe
. The visual image is great when you're referring to someone arriving at a bad time - after all, is there ever a good time to find a hair in your soup? But I find the second meaning a little odd. It seems to me that saying something irrelevant, like a non sequitur, is more like finding a hammer in your make-up kit - it has no purpose there, but there's nothing inherently wrong with it. A hair in your soup, though, isn't just pointless but also downright yucky.
J'étais en train d'imiter mon chef quand il est arrivé comme un cheveu sur la soupe.
I was doing an impersonation of my boss when he showed up.