First appearance of Marj Dusay as Blair's mother, 'Monica Warner.'
Blair's cousin Geri has always been referred to as a Warner but when Geri tells Blair's mother Monica she knows the truth about her hospital visit from her mom, Monica calls Geri's mom her sister. Monica is only a Warner by marriage & if Geri's mom is her sister than Geri is not a Warner.
This is one of the very rare episodes in which profanity was said. After Blair asks Monica what her doctor said to her regarding her biopsy for breast cancer, Monica yells "I have the damn results!"
When Blair talks with Monica about their relationship, that they're more like playmates than daughter/mother, she goes on to say they have a "deeply superficial" relationship. This isn't surprising, as one of Blair's defining personality traits is being shallow and materialistic, and her mother, Monica, is also clearly the same even going back to her first appearance in Like Mother, Like Daughter (1979). It therefore makes sense the two would have a superficial relationship.
This isn't the first episode with Blair's mother, Monica Warner. In Like Mother, Like Daughter (1979), she was portrayed by Pam Huntington.