The Muddy Hand
The Muddy Hand is a disembodied hand made of mud that appears in one of Rodrick's horror movies entitled "Hello, You're Dead". In it, the Muddy Hand travels the countryside looking for victims to strangle, and the last person who sees it is always the next victim. The film in question freaked Rowley out, and Greg at the end (where the Muddy Hand strangles its last victim and walks straight at the screen, implying that the viewer was its next victim). This made Greg and Rowley paranoid that the Muddy Hand was out to get them (despite being a fictional character). Greg then implies that since it is just a hand it would take a long time to get to them so they stopped worrying about it. It was only mentioned in "Dog Days". In Rodrick Rules, The Foot is used (which is most likely a parody of the Muddy Hand).