In my wife’s family putting peas in it is my a time-honored tradition. They even sing a little song: “Eat that mackie cheese and peas,” or “Eat that mackie cheese, no peas,” depending. Especially camping - they use dried peas which get rehydrated by the time it’s cooked. The one additive they also like that I can’t stand is tuna. In a sandwich, great, but not in my mackie cheese pleeeze.