I just ran across a reference to this article by Alex Sandler, on how C++ implements "object-oriented" concepts.

It's a more detailed, and probably more recently researched, coverage of a topic I briefly covered in my RubyConf 2008 talk. If you understand this stuff, you have an appreciation why a compile-time static typed, run-time weakly typed language like C++, as compared to a run-time typed language like Ruby or Smalltalk, makes it crucial to avoid tricking the compiler into thinking that an object is of the wrong type.