Of course, you know this means war!

A declaration of all-out revenge made after being slighted or injured by another party. Usually used humorously. Popularized by the Looney Tunes characters Bugs Bunny and Daffy Duck, likely in reference to The Marx Brothers. A: "Sarah told the Bobby that you were allergic to his cat so that she'd have a shot at dating him." B: "She did what?! Why, that no-good, rotten… Of course, you know this means war!" So, they think they can push us around with their lawsuits, eh? That we'll just roll over and let them have our property? Well, of course, you know this means war!