Ruby (programming language)
Ruby has been described as a multi-paradigm programming language: it allows procedural programming (defining functions/variables outside classes makes them part of the root, 'self' Object), with object orientation (everything is an object) or functional programming (it has anonymous functions, closures, and continuations; statements all have values, and functions return the last evaluation). It has support for introspection, reflection and metaprogramming, as well as support for interpreter-based threads. Ruby features dynamic typing, and supports parametric polymorphism.
TOM (object-oriented programming language)
It is this latter ability that represents "the whole idea". Unlike Objective-C's categories that allowed only new methods to be built onto existing classes, TOM allowed the addition of class and instance variables, new methods, even new superclasses. This results in the redefinition of "class" as "a class is defined by its main definition and any extensions", these extensions have become a first-class citizen of the language (similarly to Ruby).