Dr. Mueller is an unseen character only mentioned in the North American and European instruction manual of Splatterhouse 2. He was once a scientist doing experiments with the strange monsters found near his home. In the instruction manual for the game, it's noted that he found some other weapons used in the game and even caught a Screaming Mimi. Outside of the journal entries, he is not mentioned at all. However, he is believed to be the flask-tossing zombie monster at the end of Stage V,
whose fate is to be torched with a potassium bomb or splattered all over the floor with a single punch. Since Dr. Mueller does not exist in Japanese sources, the Japanese fandom generally believes that this boss is instead supposed to be a transformed West, although this is unconfirmed.