We did this when we brought our cats over a couple of months ago. Food & bowls, vet paperwork, a couple of toys + some throwaway litter boxes all attached in some way to their carriers. (Technically the carriers were sitting in the unopened disposable boxes.) The agent told us that it was completely fine as long as everything was within the allowed weight limit. We were just shy of it, but already knew that before arriving. I don't care how ridiculous we probably appeared to strangers. Having those throwaway boxes when we first arrived helped a ton.