Hallie is Bacteria Boy's® funky, foul-smelling girlfriend. She's always been a real stinker, and loves to surround herself with mischief. Hallie and Bacteria Boy met when they were little rascals attending Molar Towne® Elementary. They often skipped class, and were placed in detention for chewing bubble gum when their teacher, Ms. Molar, wasn't looking. As Bacteria Boy's bad habits and troublemaking increased, Hallie fell even harder for her bully boyfriend. She always looks like a hot mess with her scraggly two-toned hair and jagged yellow teeth. Her breath is as potent as poison, and she is always hitched to Bacteria Boy's® hip. Hallie enjoys being on the bad guy's side, because naughty is her middle name and being smelly is her game! She is a stubborn gal who refuses to brush or floss her teeth. No wonder her breath reeks so bad!