HOLLY ELIZABETH HILLS is HEATHER HILLS' younger sister. She's the most popular girl in GREG HEFFEL'S grade, but is considered to be the fourth-prettiest girl in their grade . It was revealed that when she was the only four year old in preschool who wasn't potty-trained, as told by SUSAN, as shown in The Last Straw, when GREG and ROWLEY were going to the Roll-A-Round roller rink in SUSAN'S car. although this most likely is a lie.