Of course, such departures vary according to circumstance. If said character has 'sensationally quit', then we hear the usual declarations of theatre aspirations ('real' acting), tv presenting (loads of cash) or, most hilariously, Making it Big in Hollywood (just delusional).
If the axe has fallen, we get the initial devastation, quickly followed by an announcement that it was by mutual agreement, that the character had gone as far as he/she could go, blah, blah, blah.