Now I know where the term Y Combinator came from. Am I the only ignorant one here who had never heard of "The Applicative Order Y Combinator"?

JavaScript:

function Y(le) { return (function (f) { return f(f); } (function (f) { return le(function (x) { return f(f)(x); }); })); }

Trippy recursive function, but I don't think I quite understand what you would use it for. ;)