Celery
See flannel. A good metaphor for bad legal writing: it does no harm, but no good either[1]. If you go to the store, celery is on your list, and they have none, it is not something you feel the need to die in a ditch about.
Celery comes in all shapes and sizes, and can go limp if left unattended.
A word on thermic energy and the calorific negativity
From the perspective of metaphorical purity it is, alas, not true that eating celery burns more calories than it provides. It is not a negative-calorie food. A stalk of celery yields 6 calories, but we expends only half a calorie digesting it. Thus, celery has a “thermic effect” of about 8%, and would need 100% or more to generate “negative calories”.
Despite its recurring popularity in dieting guides, there is no scientific evidence supporting the idea that any food is calorically negative. Sorry to prick that bubble, fellahs.
See also
Plain English Anatomy™ Noun | Verb | Adjective | Adverb | Preposition | Conjunction | Latin | Germany | Flannel | Legal triplicate | Nominalisation | Murder your darlings