Veggies are easy to spot...
Crew: "Mr <<insert name>>, would you like something to eat? I can offer you a parma ham salad or lamb casserole."
Mr Op-up: "Well, actually I was most fortunate having received an op-up at the gate and was wondering if it might be possible to have a cheese sandwich from the back"
Crew: "Not a problem, just give me a couple of ticks whilst I go rummage in the rear galley for you. If you are happy to take this tray now, I can fix you a drink. Another Bloody-Mary?"
Mr Op-up: "Thank you so much, you are most kind"
Crew returns to Mr Op-ups seat with sandwich, quartered and plated.