Before coming back to his hometown of Tianjin to visit his grandfather Chen Weizhen at the care home, Chen Zhuo worked in the cross-border e-commerce sector in Guangzhou, Guangdong province.

"My grandpa has been diagnosed with Guillain-Barre syndrome, which is a rare neurological disorder where the nerves are attacked by the immune system. It causes weakness and tingling in the arms and legs," Chen Zhuo says.

"Although he has recovered, in the worst case scenario, he might only have been able to move his eyelids and mouth. I want to be with him in his later years. I don't want to regret missing this time."

Chen Zhuo previously had no idea what care homes were like. He visited the care home with a sense of curiosity in March last year. During the first month, he observed that the residents' lives are like in kindegarten. They follow a strict schedule regulating what they eat, and when to rest and exercise.

With a major in radio and television scriptwriting and directing from Tiangong University in Tianjin, Chen Zhuo used his skills to record his grandfather's life in the care home and posted videos on Douyin.

Later, he began to stage amusing situations involving a set of characters.

The first viral video was from his Lessons in Chemistry Experiments series, in which the "teacher" sets the tone in the classroom. Yu actually worked as a chemistry teacher at Tianjin Yaohua High School before retirement.

In one episode, Yu asks Carl to identify a gas. Only after Carl directly snorts the fumes does the teacher remind him that the gas, which reeks like rotten eggs, is toxic hydrogen sulfide, and so he should cup his hand above the container and waft it toward his face rather than put his nostrils on the container's lip and inhale.

Still clad in his school uniform, Carl is carried off on a stretcher and arrives at Nantianmen (Southern Heavenly Gate), the main gate of the Jade Emperor's palace in heaven.

At the gate, Buddha asks Carl: "Why have you come?" With his hands behind his back, Carl answers: "My chemistry teacher sent me."