Need cats? Have kittify.

kittify bookmarklet

/* Highlight everything below, drag to bookmarks bar */
javascript:(function(b){var a=b.getElementsByTagName("img"),f=a.length,d,c,e;for(d=0;d<f;d++){a[d].src="http://placekitten.com/"+a[d].width+"/"+a[d].height;}})(document);

kittify.js

(function (document) {

	var images = document.getElementsByTagName('img'),
		length = images.length,
		i,
		w,
		h;

	for (i = 0; i < length; i++) {
		images[i].src = 'http://placekitten.com/'+images[i].width+'/'+images[i].height;
	}

})(document);

kittify.min.js

(function(b){var a=b.getElementsByTagName("img"),f=a.length,d,c,e;for(d=0;d<f;d++){a[d].src="http://placekitten.com/"+a[d].width+"/"+a[d].height;}})(document);