Bernadette Peters plays Karen's sister Gin. Earlier in the series, Jack stole a lock of her hair to make a wig of Broadway performers' hair.
Josh Lucas, who guest stars, was previously mentioned in episode "Buy Buy Baby."
When the group is surprised Karen has a sister, Karen says she talks about her all of the time. Her name is Gin, short for Virginia. She also has a brother-in-law named Johnny Walker. Both are types/brands of alcohol.
Josh Lucas guest stars in this episode. Later he and Debra Messing star in The Mysteries of Laura and play ex-spouses.