Smoozy Lilly is Mark Lilly's older sister. She is only mentioned by Mark in the series. He brings up his sister to Callie Maggotbone in the episode "Mark Loves Dick".

Mark says that Smoozy lost job after job, and people blamed it on her sweating problem, which stems from her overactive skunk glands in the armpits. But he believes she lost those jobs to sexism.