Malcolm in the Middle - Season 5 Episode 13
Lois's Sister

Lois younger sister, Susan, 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 for dumping her for Lois. Lois and Susans 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.