In "Wild Thing", everyone's sickness of Adam's constant complaining was finally replenished, when a new student arrived and acted entirely opposite to him, by keeping her mouth shut. The unnamed new student, referred to as "Possum Girl" or "PG", was obviously a human pretending to be a possum, but only Adam knew about this. Adam quickly became jealous of Possum Girl's uprising popularity, but when trying to explain her falsehood to everyone, they ignored him, either because they were too stupid or because they just wanted to believe she was an animal, so they could spend more time with a human who wasn't Adam. Though the former is usually the case in these situations, the latter could easily be true, as Adam's friends all sat around the table and trash-talked him in comparison to the now praised Possum Girl.
When Adam was alone with Possum Girl, Adam threatened her, saying that CDMS was his school and he would not tolerate her replacing him. The Possum Girl then proceeded to slap him on the head, apparently thinking his red hair was fire. Adam explained that he was simply a ginger, but Possum Girl revealed that she could speak, ans said back to him, that she did that just because she wanted to "slap his stupid head". Adam lashed out at her, but then Mr. Mandrill slid into the scene and scolded him for disrespecting a poor animal student like her. When Adam tried telling him that she was a speaking human, Possum Girl continued acting like a mute creature, which successfully convinced Mandrill and further enraged Adam.
After Possum Girl pulled the fire alarm, making another joke about Adam's hair, the rest of the school fled, fearing a real fire. In the absence of everyone else, Possum Girl talked to Adam again, insulting his hair and his character. After this, Adam decided to take a different approach at getting rid of her. Adam asked Principal Pixiefrog for advice. He learned about a law, saying that possum impersonation was illegal.
Adam used Mrs. Warthog as a road hog to try and run over Possum Girl, knowing that if she was a real possum, she would play dead instead of actually saving her life, by getting out of the way. Being a real human being, she'd be smart enough to not get herself killed. Jake stopped Adam and made him miss his target.
Adam suspected the plan would fail from the very start and said he had a backup plan. Possum Girl then tried slapping his head once more, but this time, Adam was wearing ultra-hardening hairspray, making his hair as hard as a rock. Possum Girl chipped her nail with the slap. Possum Girl screamed and blew her cover in front of everyone. After she couldn't go any deeper, Possum Girl explained that she was a member of Adam's fan club, a series of human kids who saw him as a celebrity for going to an animal school. She then revealed that she was madly in love with him, but before she could do anything, she was arrested by the possum police for impersonation of a possum, getting her sent away forever, and in turn, ruining Adam's opportunity to get a girlfriend with more than one eye.
Possum Girl is a very pale-skinned human girl, with plain white skin and scruffy black hair. She has a ripped up dark yellow dress, ripped up lighter yellow pants, and black shoes. She also has a bunch of blotches of dirt and must all over her face and clothing. She has blue eyes.
Possum Girl is an obnoxious, antagonistic girl, with a crazed-stalker-like obsession and undying love for Adam Lyon, but being as immature as she is, she has no idea how to express these feelings, as so she just pesters him. When not pretending to be a non-verbal possum, Possum Girl is loud, whiny, bratty, and overall, very uncomfortable to listen to. She is also very vain, as she freaked out, when she chipped a precious nail.
- Possum Girl's real name was never revealed.
Grim Adventures of Billy & Mandy