S6, E21: Responding to the pleas of his father’s mistress turned girlfriend Tina (guest star Lesley Ann Warren, "Victor/Victoria"), Will (Eric McCormack) attempts to discover whether there is a new woman in his dad’s life. However, when his father’s new mistress turns out to be his mother (guest star Blythe Danner), Will must find a way to break the shocking truth to Tina. Meanwhile Elliot’s (guest star Michael Angarano) decision to try out for his high school cheerleading squad has Jack (Sean Hayes) all smiles as he is determined to help his son make the team. Debra Messing and Megan Mullally also star.