You might be looking for the word epigram. If so, an epigram is a short, well-put statement or piece of poetry, frequently amusing. Characteristic of many epigrams is a surprise, and often paradoxical, ending. A piece of writing you'd describe that way is called epigrammatic. Examples of epigrams include:
'He was conspicuous by his absence.'
'Don't believe a word I say: you know all lawyers are liars.'
'Beauty is most beautiful when plain.'
'I can resist everything except temptation.' (Oscar Wilde)
'What is an epigram? A dwarfish whole,
'Its body brevity and wit its soul.' (Coleridge)