Aside from the mainstream importance of Madd Dogg, he has been established into a lesser-known myth figure as well. Mad Doc, the original name for Rockstar New England, is said to be origin of Madd Dogg's name. It is for this reason he is often connected with the Green Goo. One of the facts states that a green substance enclosed in a conical flask is used in the official logo for the Mad Doc. This is the reason Green Goo has been interlinked to the character.
Moreover, Madd Dogg is rumored to a be concealed member of the Epsilon Program, having worked with Maccer. It may be possible that Madd Dogg was approached by the cult to cope with his drug addiction, similar to Maccer's rehabilitation.
A weird portrait of undisclosed nature is also found in Madd Dogg's mansion. The portrait features a group of people worshiping around a radiant object in the center, most likely related to bygone rituals. Madd Dogg is believed to be involved in these dark practices. However, this is yet to be demonstrated as authentic. It is also possible, that he bought it without proper knowledge. He is also said to be deceived by the Reaper.
In GTA V, a gold record similar to the one he earns at the end of GTA SA can be seen in Franklin's Vinewood Hills home. A photo of him is also found there.