Wendy's marketing team:
"Hey so you guys hear about those ghost peppers? They're a huge hit on the internet."
"Yeah everyone knows about ghost peppers, what's your point?"
"Exactly, everyone knows. So why don't do something with them? People would want to try them"
"We can't because the capsacian content is way too high. It can literally leave your mouth with 2nd degree burns. That, and we would be liable for a lawsuit."
"Well what if we just diced up some green peppers, soaked them in vinegar with lots of peppers and habaneros and told them they were ghost peppers?"
"Well...actually...That might work."
"Brilliant."
I imagine that's how this idea came about. Probably not even real ghost peppers.