In the milestone 100th episode, “Lois’ Sister,” Lois’ younger sister, Susan (Laurie Metcalf), pays the family a visit and brings with her expensive gifts for the boys, biting remarks for Lois and a cold shoulder for Hal – whom she has never forgiven ... (more)for dumping her for Lois. Lois and Susan’s competitive relationship takes a turn for the worse when Susan gives Malcolm and Reese her prize ’65 Mustang convertible. But when Lois discovers that Susan needs a kidney transplant, she puts her anger aside and offers to donate her kidney to Susan, which Susan only sees as the perfect opportunity for Lois to one-up her.

Abigail Mavity, Alyssa Monka, Chanel Gaines, Gracie Markland, Hayley Erin, Heather McPhaul, Jasmine Di Angelo, Josh Jacobson, Kate Lang Johnson, Kevin Cooney, Laurie Metcalf, Lyndsy Fonseca, Montana Tsai, Tianna Danielle Kenney