On December 16, he made a guest appearance on “Running Man” where he had the opportunity to solve various missions with main members of the show. He earned his special nickname on the show after he showed that he was in no hurry to get anywhere, even after completing missions. He would walk by foot to locations and on the way to locations where the missions would send him, he would fall asleep. And even after failing a mission, he would always be strutting casually on foot unbothered.
So for that reason, “Running Man” member Yoo Jae Suk called Go Soo a “turtle” which everyone approved. However, Go Soo was not in the slightest bit affected by their teasing and continued to react slowly to everything- causing everyone to laugh on the show.