Gwen is a main character from "Monster Shaker". As Justin's older sister, she tends to make fun of her nine-year-old brother, though the two of them do have a good bond with each other. Additionally, the two of them must work as a team to patch up the damages created by the monsters from Justin's magic shaker, while keeping the object hidden from others. She has reddish-brown hair, and is mostly seen wearing a dark pink shirt and purple pants, although her shoes are light brown in color.