Room 101: The Miracle of become:. One of the corners where Smalltalk clearly differs from all other languages I have had to do with so far (except Common Lisp, but that's different, because everything is possible there), is the become: method, with which two objects in the running system exchange their identity - so that after the call all references to a after a become: b then refer to b and vice versa. This explains what this means in practice.