Anything that makes you laugh. But the finest sort draws a tear along with the laugh. – George Bernard Shaw                              

Humor, however broad and genial, takes a narrower view than enthusiasm. – Thoreau

Shall I crack any of those old jokes, master, at which the audience never fails to laugh?  – Aristophanes, Frogs

I can tell undoubted Raphaels from Gerard Dows and Zoffanies.
I know the croaking chorus from The Frogs of Aristophanes! – Major General Stanley

Brevity is the soul of wit. – Hamlet Prince of Denmark, Act 2, Scene ii

Humor is also a way of saying something serious. –  T.S. Eliot

Everybody likes a kidder, but nobody lends him money. –  Arthur Miller

We are not amused.  – Queen Victoria

A jest’s prosperity lies in the ear of him that hears it, Never in the tongue of him that makes it. – Love’s Labors Lost, Act 5, Scene ii

Among those whom I like or admire, I can find no common denominator,
but among those whom I love, I can: all of them make me laugh. –  W.H. Auden