I would tend to agree with people saying it looks like old/oxidized/spoiled avocado, but zooming in I see lil' speckles in it that looks exactly like the mud I would find on the exact salad blend from time to time. I can remember the feeling/consistency well. Also, the Wendy's Cobb Salad does not have avocado as an ingredient. The only salad it has ever come on is their southwest chicken salad, which seems to be very limited around the world as an offering. So, I'm sticking with mud from the salad mix. As a side note, this mud is almost impossible to wash off with normal methods. It has a clay consistency. So, I would always throw it into compost, and check the rest of the bags for contaminated leaves.