Eva is the deuteragonist of Igor. She is voiced by Molly Shannon. Originally, Igor intended her to be a weapon of chaos and destruction, but she was accidentally brainwashed into an actress by one of Igor's original creations Brain. Near the end of the film, she is later seen destroying the enemies from the arena in the Igor Recycling Center and is now friends with Igor.
With Brain and Scamper's help, Igor assembles a huge, monstrous being from human remains. When he brings her to life, however, he discovers that the "Evil Bone" he gave her was not activated, making her kind, friendly and feminine. Igor tries to convince her that she is evil, inadvertently naming her "Eva."
Igor attempts to brainwash Eva into becoming evil by bringing her to a brainwashing salon where people are hooked into a machine and shown monster movies for a few hours. Brain also gets the same thing in order to watch TV, but he has taken the remote for Eva's room and every time he tries to change the channel the TV in Eva's room changes. She therefore watches the movie Annie for several hours, so when Eva gets out she can speak English and wants to be an actress. Igor then takes her back to the castle to be destroyed in the car. On the way back to the castle, Igor's nemesis Dr. Schadenfreude and Jackie try to steal Eva by using a shrink ray to shrink them all, but are instead struck by the ray themselves. Igor decides to exhibit Eva at the science fair anyway, telling her that the fair is an "Annie" audition.
Dr. Schadenfreude learns of Eva's existence and attempts to steal her. When that fails, he exposes Igor to King Malbert, who promptly sends Igor to an "Igor Recycling Plant." Schadenfreude activates Eva's Evil Bone and unleashes her on the Science Fair, where she destroys all the Evil Inventions. Scamper and Brain help Igor escape from the Igor Recycling Plant and they learn that Malbert had deliberately killed Malaria's crops with a weather ray that made storm clouds so he could implement his "Evil Inventions" plan, thereby keeping himself in power. Rushing into the arena, Igor reasons with Eva to deactivate her Evil Bone and allowing her to regain her sweet personality, while Scamper and Brain deactivate the weather ray, which falls and crushes Malbert to death.
Dr. Schadenfreude attempts to take power, but the citizens revolt upon learning of Malbert's deception. Jackie sees that her voice is cracking, so she tries to get another pill but finds she's all out. As Jackie's voice becomes more and more cracked, she transforms into a female Igor. The monarchy has been dissolved and Malaria becomes a republic, with Igor as president. Schadenfreude is relegated to pickle salesman, while the annual Science Fair becomes an annual musical theater showcase. Igor and Eva are planning on making a dog, or adopting one.