HONG KONG — China began an audacious experiment four decades ago to inject free-market thinking into its rigid, Communist-controlled political system, beginning a process that would lift hundreds of millions of people out of poverty and create the world’s second-largest economy.

And what better way to celebrate this accomplishment than with a bucket of fried chicken?

Last week, KFC introduced an advertising campaign in mainland China celebrating 40 years of “reform and opening up,” the catchphrase that defined the era. A two-minute TV spot that aired on state television showed two Chinese celebrities traveling back in time by railway, seeing streets filled with bicycles and bamboo scaffolding.

The actors are then jolted back into the present on a high-speed bullet train to sporting events that evoke the 2008 Summer Olympics in Beijing and to young people using smartphones and cheering at pop music concerts. As the ad continues, it shows people carrying boxes and buckets of KFC, with one group of twentysomethings clinking chicken nuggets together as if toasting with champagne.

“Who would have thought that the past 40 years would bring so much change?” one of the stars, the 44-year-old actor Huang Bo, says to Lu Han, a 28-year-old Chinese heartthrob. The TV spot concludes with a voice-over “saluting” China’s 40th anniversary of economic reform and a cheer of “Go, China!”