Celery is the most occult food.

I'm not accustomed to finding symbols in my dinner. I have never, for example, seen the face of Jesus on my cheese, or Michael Jackson on a biscuit. I had terrible trouble eating a Lindt Easter bunny once, but that was because it regarded me askance with its terrible flat brown eye. Its little neck ribbon would jingle at me, accusingly. Since then, I've got over myself, and will happily eat a thing with a face, especially if that thing is a Percy Pig (I'm not anthropomorphising pork here; I do mean the sweets).

What does it mean when letters of the Greek alphabet start appearing carved into your salad? Is the world going to end, or does the staff of Tesco contain a bored and subversive classics student, secretly scribing "get me out of here" across the fresh produce?