Though Mills never made any money off the idea, friends said he was thrilled just the same that it came to fruition.
Mills began the grassroots campaign because he regularly used the cheesy corn chips Doritos as shells for taco salad and always maintained the chips made into taco shells would be a winner. He wrote a letter to Frito-Lays and was told thanks, but no thanks, USA Today reported Wednesday.
Mills started a Facebook page promoting the idea and used his graphic design skills to craft images of celebrities and inventors holding Doritos tacos. The images included Albert Einstein with a thought bubble and a vision of the taco in it, Apple founder Steve Jobs with the taco on a computer screen and Chuck Norris doing a karate kick while eating the taco.
The page eventually garnered some 4,200 "likes" and got the attention of Taco Bell executives. In 2012, they wrote Mills a letter saying they had put his idea into development, calling them Doritos Locos Tacos -- and invited Mills to their test kitchen in California to sample one.
The idea has been a sensation, with the company reporting more than $1 billion in sales this year, USA Today said.
Mills worked at his local chamber of commerce in Little Rock, Ark., until August, when his cancer diagnosis forced him from his job. Mills underwent two brain surgeries and a lung surgery before dying on Thanksgiving, his wife, Ginger, said.
Upon news of Mills' death, friends began posting pictures of themselves eating Doritos Locos Tacos on Facebook.
"It was a sweet memorial," Ginger Mills said.
Calling Mills a "true friend" of the company, Taco Bell released a statement offering its condolences.
"We are honored to have had his support through the Doritos for Taco Shells Movement on Facebook, and we admire his strength and optimism during his recent battle. Our thoughts and sympathies are with Todd's family during this time," the company said.
In addition to his wife, Mills is survived by two daughters: Tyler, 19, and Lainey, 6. His funeral was Monday.