Lay out the 8 slices of bread on a work surface. Spread half with ketchup and half with mustard.
Place a slice of American cheese on the mustard slice of bread and a slice of mozzarella cheese on the ketchup slice of bread.
Cut the hot dogs in half longways so they are thinner and quicker to heat. Cut in half to shorten. Tip: If cooking with kids, consider preheating the hotdogs then the kids have less pressure to heat the hotdogs, but just brown the bread and melt the cheese.
Divide the hotdogs evenly on the mozzarella cheese, then close the sandwich with the cheddar cheese.
Place one sandwich in a pie iron, close, and clip shut. Place over a campfire's coals and cook for 10 minutes, turning every 2 minutes to make sure it heats through.
Crack open the pie iron to see if the bread is browned, if not close and continue cooking until done. Once done turn out onto a plate and let cool for 5 minutes before eating.