The mask prop is not only a symbol for the Thin Kid character and Horror Movie’s cultural legacy, but it is also a motif that drives Blurring the Line Between Art and Reality as a theme. The mask is initially depicted as a malleable object. In the Horror Movie screenplay, the mask keeps changing forms, which is meant to foreshadow the malleability of its wearer. The longer the Thin Kid wears the mask, the more he transforms into an actual monster. 

This quality bleeds into the real world as the narrator reports his ability to transform into the Thin Kid monster and then the new actor playing the Thin Kid by the end of the novel. It is a challenge to question whether the narrator is being honest by the end or if his story is compelling enough to convince the reader that the truth doesn’t matter. This also resonates with the mask’s mysterious origins, which Tremblay injects with ambiguity throughout the text. While it is possible that Cleo could have constructed the mask herself, her insistence that she had found the mask in an abandoned school is the seed of the mythology that grows around Horror Movie.