Karen Griffin is the main antagonist of the Family Guy episode "Peter's Sister". She is Peter Griffin's abusive older sister and a wrestler who performs under the name of "Heavy Flo".
When she drops in to visit for Thanksgiving, Meg discovers that she treats Peter the same way that he treats her. Although amused at first, she realizes that Karen takes things too far and decides to work with Peter to even the odds.
Karen's physical and emotional abusive treatment of Peter is very much the same as the way Peter treats Meg (possibly because Meg vaguely resembles Karen) and a clear explanation of Peter's own abusive behavior, not only to Meg but to everyone Peter disregards in his unpredictable escapades and mayhem, which so very often causes someone some form of pain and/or misery. In other words, Karen is somewhat responsible for her brother being the man he is today.
- She is voiced by Kate McKinnon.
- Karen is very similar to Grandma Stotch.