A flea and a fly in a flue. Said the flea: "let us fly", said the fly: "let us flee" and they flew through a flaw in the flue.

In Dutch the word order is a bit better: als achter vliegen vliegen vliegen, vliegen vliegen vliegen achterna.

In german you can also say: Wenn hinter fliegen Fliegen fliegen, fliegen Fliegen fliegen nach. : )