Add Snapchat.js to your page, and you'll be able to scribble all over it.
I'm using this as a bookmarklet in Chrome. You can too!
javascript:var script=document.createElement('script');script.type='text/javascript';script.src='//brandly.github.io/Snapchat.js/snapchat.min.js';document.head.appendChild(script);Some sites won't let you inject scripts, though. 🐙