My very favorite telling of the Malcolm Tucker origin story. When Peter walked into his first meeting with Armando, Malcolm existed only as a name and a vague idea – he had no face and more significantly no voice. There was no script for Peter to learn and no lines prepared to give him any idea what Malcolm was expected to sound like.
But all it took was one single improvised scene (with Armando as the hapless minister) and Malcolm was THERE. I’m sure bits and pieces of him were tweaked before filming started, but the instantly recognizable *truth* of him came to life in that single instant when Peter first found within himself Malcolm’s words that turned Peter’s face into Malcolm’s face when he spoke them.