[sisk]

Here, this one will work without requiring jQuery:

  javascript:(function(){var a=document.getElementsByTagName('img'),i=a.length;while(b=a[--i]){b.setAttribute('src','http://placekitten.com/'+b.width+'/'+b.height);}})();

[gregschlom]

Thanks. Perfect match with http://ft.com and http://nytimes.com. Gives me a good laugh :)