San E worked out his chest hard after listening to Kim Jong-kook's advice

Choi San appeared as a guest on Running Man haha.

It's also so cute when he transforms into the Grand Duke of the North and lets out a hollow laugh while delivering his lines.

He said that he worked really hard on his chest exercises after Kim Jong-kook gave him advice in the past.

For the 'Bad' choreography, the facial expressions and physique seemed to be in perfect harmony.