One thing I really like about python is that the language (syntax, parser, compiler, interpreter) itself is actually very small. A lot (75%0 of the functional code that I end up actually debugging and reading is just plain old python stuff that most of us can understand.
Aside from the runtime stuff, most of the python interpreter is just a bunch of python objects that anyone can mess with. If I remove a dict entry from sys.modules, the module is reloaded. __import__ is just another python callable. Lots of core functionality is implemented as extension modules, like codecs, _codecs and posixpath.
To a degree this speaks to the integrity of the language itself. As I understand it a project like pypy would test the language to the max, being able to implement itself within itself. I think the thinness of the core python code and the thickness of the 2nd layer of interpreter logic on top of that is equally interesting.