Hank Hill has been shown throughout the series to have a deep interest in propane and propane accessories, but why? It all began years ago when Hank was still a young boy.
Hank first encountered propane when he was 12 years old and his parents left him at a neighbor's house for the weekend. His parents had sheltered him from propane as they preferred charcoal and feared the effect it might have on their child. It was only natural that Hank would be drawn to its strong aroma as neighbor Dave lit the grill. "Now that smells good I tell you H'Wat" Hank exclaimed as he ran outside and onto the patio. Dave had gone inside to get the steaks and Hank was alone, Just him and the propane. It was at this moment that Hank's love affair with propane and propane accessories would begin.
Hank spent the following months sneaking out of the house at night to visit Dave's patio and breathe in the intoxicating fumes created by that heavenly fuel. This continued for nearly a year until Cotton discovered Hank's nightly visits as he took out the trash. He was furious with Hank for allowing propane to control his life in this way. He sent Hank away to boot camp in hopes of separating him from propane. This was met with little success. Although the camp only used charcoal grills, Hank was able to smuggle in a bottle to last him throughout the duration of the camp. When he returned home his love for propane was stronger than ever. This tarnished his relationship with Cotton forever, as seen throughout most of King of the Hill.
When Hank graduated highschool and decided not to go to college in favor of pursuing a career in propane Cotton only grew angrier. From here we move into the events of King of the Hill.
There you have it. The origin of Hank Hill in all its glory.