for over two decades we have been proving identities involving plethystic operators (vertex operators for some people) by manipulations which politely could be called ``heuristic''. but deep down i felt them to be quite ``fishy". but referees accepted them and we felt nevertheless confident since we always got the right answer, as amply confirmed by computer experimentations. but suddenly this summer an example popped up where our manipulations yielded a patently false answer. panic? yes ... for a while. in this talk we will present how in the end all of this finally, and belatedly could be made completely rigorous.