Shelley appeared in the episode "The Tale of Oblivion". She was portrayed by Emma Taylor-Isherwood (although she was credited under the name Emma Isherwood).
Shelley is the twin sister of Max, and is portrayed as the more mature and responsible of the pair. Where Max had to be woken up by their mother
and reminded to clean his bedroom, Shelley was already awake and eating breakfast and had cleaned her bedroom, prompting Max to tell her to clean his as well. Similarly, when their neighbor's dog, Butch, approached them while walking to school, the dog was incredibly friendly to her, but was hostile to Max. Shelley was highly resentful to Max's claims of the fact she was a "barnacle" due to the fact that, as twins, they were in the same classes and had the same group of friends.
During art class, Shelley was the first to notice the fruit disappearing as Max erased it with his magic art supplies, and commented that people should "at least wait until lunch time," to eat, rather than ruining their art project. That afternoon, when she and Max were at home, she learned about the magic tools when Max demonstrated their power by showing her Butch's collar, then erasing their piano to get out of lessons that afternoon and, finally, her underwear. Concerned over what he might do next, Shelley phoned their mother at work, but was erased mid-conversation.
She was next seen imprisoned by the viking warrior Kronos in the Oblivion Realm, where she was being held hostage in exchange for Max's art supplies. She and Max made amends after Max, overcome by guilt for erasing her, tricked Kronos into thinking he was getting the supplies, but actually erased all of Oblivion, save for the twins, the magician Sardo and Butch. When they returned to the real world, Shelley covered for Max by claiming that Sardo was a piano repairman, and that they had not cleaned the house because they were dog-sitting Butch.
- Emma Taylor-Isherwood also portrayed Julie.