GreaseMonkey has always been powerful. It's a Firefox extension that gives you the ability to customize the HTML etc that gets displayed in the brwoser - you needn't be constrained by what gets served up. I've previously played around with a bit.
But, unless you were able to use an existing script created for a well-known page, or were willing to get in and edit a script by hand to create or tailor, GreaseMonkey hasn't been particularly accessible to the masses.
Enter Platypus, another Firefix extension. Platypus is as a WYSIWYG editor for creating GreaseMonkey scripts. After installing both extensions, when visiting a page that you want to customize (e.g. remove some screen components, rearrange components, etc), you use the Platypus toolbar
to make your desired changes, and then 'Save' those changes to a GreaseMonkey script. The next time you visit that same page it will appear as you customized.
As an experiment, I used Platypus to customize the login page at Sxore (chosen because it, in its unmodified form of supporting multiple identity systems/options, demonstrates the potential for user confusion about identity options). I removed all screen elements but the 'Log in with OpenId' option to remove some of this confusion. The result is below.
Irrelevant (for me) options are removed. Others would tailor to suit their tastes.
Beyond removing some visual identity clutter, allowing users to tailor the identity components of pages would act as a poor-man's anti-phishing mechanism. If I were to visit a phish site purporting to be Sxore, the GreaseMonkey script would not kick-in and I'd see the default interface, possibly clueing me into alertness.
The platypus belongs to the monotreme family of mammals, distinguished from other mammals by the fact that in the monotremes a single opening (the cloaca) serves for urination, defecation, and reproduction. Perhaps then the relevance of Platypus's name to identity is to hilite the danger of overloading a single interface.
Monotreme's are also characterized by the fact that females lactate from openings in their skin as opposed to defined nipples. No analogy comes to mind.