Sylvia Svelte (voiced by June Foray) is a woman who once ran a scam of selling "nutritious food" to people looking to lose weight.
Sylvia has long blonde hair, and wears a light blue color collared short-sleeve shirt, blue pants, blue socks and blue shoes.
Sylvia is initially shown to care for people's health, as she introduce her new line of diet food. Off-camera, she is shown to be a con-artist who tricks people in order to buy her food. She is also a bit gluttonous, as she love to eat junk food.
Sylvia appeared on a half-hour infomercial about her new diet plan, claiming it to be both healthy and delicious, which attracts the interest of Jon (who was trying to diet), Garfield and Odie. After the trio arrived at Slyvia's Diet Center, Sylvia gave them sampler packs, which Jon reluctantly buys after seeing the high price. As she waved goodbye to Jon and the others, she informed her assistant to get her some junk food.
Later that night, when the dissatisfied Jon and Garfield returned to The Diet Center for a refund, Sylvia informed Jon that there were none, and called in two goons to throw Jon and Garfield out as she prepared for another commercial. Whilst doing so, she began to smell delicious food (courtesy of Garfield) resulting in her showing her true self as she dismissed her diet plan and started to eat a pizza in front of the audience and looked for more of the food she smelled earlier. Whilst joining Garfield in his indoor picnic, she thanked him and agreed to refund all of her customers' money.