Revealing mistake: Once Victoria has drawn her bath, we see her get in, and then lean back into the water. However she is already wet on her chest and her hair is damp already. This is probably due to previous takes of the same scene.
Continuity mistake: When Amy is introduced, she is writing about two lines down from the top of the page in her journal. After Troy snatches it, the writing runs about halfway down the page. (00:00:35)
Continuity mistake: As Victoria is being drowned in the bathtub, she appears very deep in underwater shots and only a few inches down in overhead shots. (00:26:00)
Answer: No, there is no such character in the comics. He's a "meteor-freak" like all the other baddies on the show. The sound has something to do with him vibrating his vocal cords very fast to create a high-pitched squeal.