In her youth, Piella was very slim and conventionally attactive, and made her name by starring in the commercials for Bake-O-Lite slimming bread, becoming known as 'The Bake-O-Lite Girl' who normally rides a balloon and always says, "I'm light as a feather, I'm the Bake-O-Lite Girl". Her fame even gives her a fortune to live in a luxurious mansion with her dog, Fluffles, which houses many mementos of her former glory. At some point, presumably before she was fired from Bake-O-Lite, she dated Bernard Grubb.
However, when Piella gained weight after eating too many bakery products and became too heavy to ride the Bake-O-Lite Balloon, she was fired. This made her snap and hate all bakers. She now decides to eliminate all bakers in the vicinity to get her revenge and to complete a baker's dozen, 13.
She pretended to fall in love with bakers and murdered them. She attempted to kill Wallace, but was angry when Gromit and Fluffles foil this attempt. She tried to escape in the Bake-O-Lite balloon but the attempt failed as her significant weight proves too much for the balloon to remain afloat, causing it to land into the local zoo's crocodile enclosure where she is eaten.
As Wallace then mourns her death in spite of her murder attempt, a younger and thinner version of herself is last seen riding the Bake-O-Lite Balloon, ascending into the heavens - possibly signifying the long-lost good in her finally coming back through.
At first Piella comes across as being a sweet-natured woman, but her true colors kick in as she is in fact, a cold, calculating and ruthless psychopath, obsessed with getting revenge. She is very cruel and controlling towards her dog Fluffles and will go to great lengths to achieve her goals. She blames baked goods in general and bakers for her situation rather than herself or the Bake-O-Lite company, is quite delusional and becomes increasingly unstable towards the end of her murder spree; she was so determined to kill Wallace, she was even prepared to detonate a bomb inside his house, which would likely have killed or injured many other people too.
She has white earrings, white necklace, pink high-heel shoes, pink dress, blonde beehive, red lipstick and blue eyelids.
- Piella was probably named after a pie with ice cream on top called Pie à la Mode, and bakewell tart. Another possibility for her first name is paella, a Spanish rice dish.
- Piella is currently the final villain in the franchise.
- She is also the only villain to die on-screen, being eaten by a crocodile, although how it occurred was never actually shown.