“When did he get so jacked?” — Good Boy fans in frenzy as Park Bo-gum showcases dramatic shift from past roles with muscular physique & brawny stunts 

On May 31, 2025, Park Bo-gum returned to the small screen with the premiere of Good Boy on Amazon Prime Video. In the show, he plays Yoon Dong-joo, an ex-Olympic boxing titleholder who joins the police force following personal hardships.

One particular moment from the premiere episode has caught widespread attention. In the scene, Dong-joo gets splattered with mud by a speeding vehicle.

He walks up to the car to address the driver and slides his arm through the open window. The driver quickly rolls the glass up, clamping Dong-joo’s hand inside while his body stays outside.

As the vehicle begins to move, his arm stays trapped in it. His legs then lift off the ground and get caught on the vehicle’s side mirror. He is carried in that position while the car drives ahead.

This sequence has gone viral across digital platforms. Viewers have been sharing the footage widely, with many spotlighting Park’s muscle power in the stunt.

"When did he get so jacked?" an X user commented.

kyle 🐑 😌

@lamb_institute

When did he get so jacked?

Park Bo-gum’s portrayal of Yang Gwan-sik represents a significant shift from his earlier portrayals. In When Life Gives You Tangerines, he takes on the role of a devoted and reliable companion who aids Oh Ae-sun (IU) through cultural and domestic obstacles.

His prior characters include Choi Taek in Reply 1988, Sa Hye-jun in Record of Youth, and Prince Lee Yeong in Love in the Moonlight, where he embodied more reflective personalities.

"Brooo since when he's build like that??" a fan remarked.

"Why is this an hour long?" a user mentioned.

"Oh mr park i was not familiar with your game," a person shared.

More fans have reacted similarly.

"I keep seeing this since yesterday and i just kept scrolling. wdym it's park bogum?" a netizen said.

"Damn, that hamstrings! 🔥," a viewer noted.

"I thought in this scene Dongju would run dragged by the car like in most dramas/movies, but it turned out that his legs was lifted to the rearview mirror, so his injury wasn't too serious, very clever🔥," another fan added.

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Park Bo-gum on his intense preparation for Good Boy role

Last year, Park Bo-gum spoke to Elle Korea about the intense preparation and physical demands of his Good Boy role, offering a look into the effort behind his transformation.

Portraying Dong-joo, a spirited and driven figure in the current drama, the actor mentioned that frequent action sequences have made shooting quite rigorous. Still, he stayed focused and fully committed to the role.

He also discussed the major shift in his appearance to reflect that of a pro athlete. To fit the part, Park switched to a strict diet of lean proteins and greens, and toiled on expanding his muscle mass. Though the change in eating habits was hard at first, he said he had adapted to it.

“I controlled my diet and increased my muscle mass to look like a national team member. At first, it wasn’t easy to do my daily routine while eating only protein and vegetables, but I’m doing my best in the given circumstances," the 31-year-old added.

Park also pointed out how much he admired those who maintained their fitness and diet with discipline over time. The South Korean artist also expressed his concern for the entire crew’s safety.

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According to Nielsen Korea, Good Boy's first episode earned an average nationwide viewership rating of 4.8 percent. The solid debut signals a strong start for the series, which blends fast-paced action with light-hearted humor.