No, of course not. They invited, and if their work fridge is anything like mine, any leftovers will get pitched in a week. You are keeping things from going to waste.
Now for my random...I'm on vacation at the beach, and have had only 1 day of sun. Unfortunately, I failed to reapply SPF after taking a beating in the surf, and now I am so toasty it will be unlikely I will be enjoying the last 2 days of the week, which are supposed to be fairly nice.