Mmm... Rat stuff.

If I may go back to "I smell a rat"...
I was working late one night in a relatively abandoned building when I noticed a horrible stench. Seconds later a rat appeared rummaging through some trash nearby. Needless to say, the saying has a very concrete origin. I think it's a gland thing.

And one more on the "French" side, as I haven't seen this on the board yet...
The classic, "Rat b*stard!" A tongue-in-cheek favorite of a few of my friends.