Zombie Jane refers to the zombie version of Jane Casey which was created by Denise Simmons in "Me Carl, You Jane-ish". In the episode call, who is still trying to ask Jane out, tries to impress her by agreeing to cover up her absent in class whilst she attends a talk by a writing hero of hers. The plan backfires when the teacher of the class demands that Carl and Jane present a presentation for the class and Carl goes looking for Jane in order to get her back to class.
Its too late though as Jane has already gone in. Denise appears outside the talk and offers to help out with magic, but Carl is worried, wanting Porter to help instead. Denise ignores this and creates a clone of Jane who is Jane but without her intelligence - making her a zombie.