Static AND Dynamic Typing?

Is it possible to create a language where it's statically typed (preferably with inference) by default, but can drop to dynamic typing for bits where you need it. I seem to remember someone saying this wouldn't work. Can anyone explain why?

>>8
Static typing is indispensable when you're modifying code and APIs, letting the compiler and editor flag stuff in realtime, even when refactoring tools are used.  Real code is maintained, bedroom coder faggot.