 The sixth season episode "Lucy and the Lost Star" is the last  episode to star actress Vivian Vance (qv), but it is also one of  the episodes that Lucille Ball (qv) was not happy to make.  According to known Hollywood sources, as well as visual proof once  you watch the episode, actress Joan Crawford (qv) was often drunk  on the set during taping which lead to frequent arguments between  the stars.