Following a somewhat impoverished childhood, George Tweedle attempted to make his way in the world as an adult by seeking employment as a salesman. After being hired by an unspecified insurance company in Fawcett City, IN, Tweedle was told by his employers to push fire insurance policies to the customers. However, he found that his salesmanship tactics were unsuccessful, and in desperation, he turned to extortion to meet his quotas.
Displaying some previously unknown capability as a chemist, Tweedle created a potion that worked in much the same way as the legendary formula that transformed literature's Dr. Jekyll into the evil Mr. Hyde. The potion, when ingested, made Tweedle taller, heavier and younger-appearing…and also gave him the temporary metahuman ability to start fires with a mere touch. A corona of flames surrounded his body during these transformations. Using this power, Tweedle began to threaten his potential customers that the Arson Fiend might come after them and cause massive losses if they didn't have his company's fire insurance. Those who bought the policies were spared; those who still refused found their businesses and homes reduced to cinders shortly thereafter. Nor was Tweedle the least bit squeamish as to whether or not anyone was inside the buildings when he set them afire.
Tweedle was soon targeted for capture by the heroic Captain Marvel, who had a showdown with Tweedle atop an oil tanker. The Arson Fiend's flames caused the tanker to explode; Capt. Marvel survived, but it appeared that Tweedle had not, for his badly charred body was found sometime later. But before a funeral could take place, it was learned that Tweedle was still alive. He was hospitalized at the city's expense and cared for as best as possible, for a time, even though he was not expected to ever recover.
A day came when the hospital was losing some of its funding, and the facility was taken over by the unscrupulous Ebeneezer Batson, who callously ordered that Tweedle be taken off of life support unless some family member was willing to continue paying for his care. At this point, Tweedle was approached by BLAZE, the demonic daughter of the wizard Shazam, who offered to restore his power if Tweedle would fight Capt. Marvel on her behalf. Tweedle was only too happy to agree, and through Blaze's magic, his burn injuries were erased and his powers were restored without his having to use his original potion. Thus it was that the Arson Fiend returned to become a recurring menace for Capt. Marvel and the other members of the Marvel Family.
Currently, Tweedle is in prison, having been captured by the heroine Mary Marvel following their last battle. How long he will remain in prison before escaping to cause more havoc is open to question.