This will be the second series in which Katey Sagal will play Kaley Cuoco's mother. The first one was 8 Simple Rules (2002).
First appearance of Penny's mother and brother.
Keith Carradine (who plays Penny's father Wyatt) and Judd Hirsch (who plays Alfred Hofstadter) have both been nominated for Oscars - Carradine for Best Original Song "I'm Easy" from Nashville (1975) (for which he won), and Hirsch for Best Supporting Actor in Ordinary People (1980).
Johnny Galecki and Katey Sagal both appear on The Conners (2018) which is a spin off of Roseanne (1988) where Galecki also appeared in.