twitter.user.js

// ==UserScript==
// @name        ヒウィッヒヒー
// @namespace   http://lowreal.net/
// @include     *
location.href = "javascript:"+encodeURIComponent(uneval(function () {
	document.body.addEventListener("DOMNodeInserted", (function me (e) {
		var walker = document.createTreeWalker(e.target, NodeFilter.SHOW_TEXT, {
			acceptNode : function (node) { return NodeFilter.FILTER_ACCEPT }
		}, true);

		while (walker.nextNode()) with (walker.currentNode)
			nodeValue = nodeValue.replace(/twitter/gi, "ヒウィッヒヒー");

		return me;
	})({ target: document.body }), false);
}))+"()";