Olivia Mears is one of the three secondary villains of the 2009 animated horror film Alvin and the Chipmunks: Bloody Massacre and a member of a biker gang. She is voiced by Liliana Mumy in the original American English dub, who is well known for voicing Myrtle Edmonds from Lilo and Stitch series. Most importantly, she is also the rival of Jake Long's younger sister Haley Long.
In the summer of 2003, Olivia, along with two bikers named Eli Pandarus (Jonathan Freeman) and Sierra McCool (Tara Strong), travels to Monterrey Park and stops in a convenience store. In the store, Olivia takes to hassling customer named Simon Seville (Matthew Gray Gubler), having both Sierra and Pandarus restrain Simon's older brother Alvin Seville (Justin Long). Having grabbed Alvin's wallet when he attempted to throw it to Simon, Olivia taunts Simon, making Simon grudgingly ask for it back and address her as "ma'am".
After Alvin Seville accidentally mangles their motorcycles as revenge for troubling him and Simon, Olivia and her fellow bikers follow the duo back to the suburbs of Riverside. Despite being reluctant in order to participate in her friends' plan to burn down the haunted house after siphoning gasoline from a red Mazda sedan, Olivia, however, after being reassured by Sierra that nobody will get hurt, wanders off to look around. Going into the haunted house, Olivia nonchalantly begins toying with some of the equipment lying around on the second floor, eventually climbing up onto the third floor that leads to the attic. Finding and rope and rake used to hoist dry leaves, Olivia begins swinging from it for fun, catching the attention of, and annoys Pandarus, who demands Olivia to come down this instant, so they can help Sierra in her revenge plans. Unseen by Pandarus, Olivia was ultimately grabbed by Theodore Seville (possessed by Donald Walls) and pulled back into the haunted house, where Theodore/Donald stabs her to an attic rafter by the throat with a sharp pitchfork. Shortly, before Theodore/Donald kills him too, Pandarus finds Olivia's corpse, which Theodore/Donald later moves. Olivia's corpse was later found and eventually taken away by the paramedics.