I was at a dinner party where the food was served family style and thought this is a great way to share germs and antibodies! Our table had a doctor which meant I could consume a lot and get a doctor's note.
At one point, I saw the doctor picking at all the food in the communal plate with his fork. I thought, how rude? That is almost as disgusting as double dipping in the salsa dish and leaving extra crumbs in there. I paused, and then I realized why?… he doesn't believe in germ theory! Germ theory states that if a microscopic germ is present in your food, and you injest that food then you will get sick, whereas the 'other' theory, known as "Soil Theory" says that germs thrive in a toxic environment, rather than creating that toxic environment.
This means that it doesn't matter if the doctor spreads any of his germs via his fork to other members of the table because if each of us is healthy, the germs will avoid us, however, if we are sick or have a toxic environment in our bodies due to eating unhealthy food…etc, then his germs, and all the germs already on your fork will infect you..
Therefore that explains why this Doctor was double-dipping in the lamb plate! So even though Seinfeld doesn't like you to double-dip, maybe it's more funny than bad for you!
For the curious, here is what the lamb looked like (no, it was not from Butcher Bar, nor was it "organic" or "grass-fed" or "pasture raised"):
Notice the abnormal amount of fat on this cut of meat. That means the animal was probably a lazy couch potato that followed the SAD diet – Standard American Diet.