Musical Powerhouses Shin Sung-rok, Jung Sang-hoon, and Kim Gun-woo Bring Stage Drama to ‘Knowing Bros’

In a high-energy crossover of musical theater and variety television, JTBC’s Knowing Bros welcomed three of the industry’s most prominent leading men on its April 4, 2026, broadcast. Jung Sang-hoon, Shin Sung-rok, and Kim Gun-woo—the driving forces behind the musical Swing Days_Code Name A—appeared on Episode 523 to share raw, behind-the-scenes accounts of their careers, ranging from vocal struggles to high-stakes stage blunders.

The episode, which aired on Saturday night, highlighted the camaraderie and competitive spirit of the three actors. Even as the guests are celebrated for their precision and professionalism on stage, their appearances on the show revealed the human errors and unexpected transformations that occur when the curtain is down.

Vocal Ambitions and ‘R&B’ Missteps

Jung Sang-hoon provided a candid seem at the rigorous preparation required for musical theater, specifically recalling his time preparing for the production of Mrs. Doubtfire. In an effort to elevate his performance, Jung sought personal vocal lessons from the renowned singer Gummy.

However, this pursuit of excellence led to a comedic clash of styles. Jung admitted that he became too immersed in Gummy’s guide recordings, attempting to incorporate an R&B-style delivery into his singing. This stylistic choice did not sit well with music director Kim Moon-jung, who reportedly reprimanded him for deviating from the intended musical direction of the show. The anecdote served as a reminder of the delicate balance between individual artistic flair and the strict requirements of a theatrical score.

The ‘Roar’ of Survival: Shin Sung-rok’s Stage Blunder

While Jung dealt with vocal direction, Shin Sung-rok shared a more visceral experience regarding the pressures of live performance. Shin recounted a harrowing moment during a performance of Jekyll and Hyde, a role for which he is widely acclaimed.

During one of the musical’s most pivotal highlight scenes, Shin suffered a sudden lapse in memory and forgot his lines. In a split-second decision to maintain the momentum of the scene and avoid a dead-air silence, Shin opted to let out a powerful roar to mask the mistake. While Shin viewed this as a successful tactical recovery, his fellow guest Jung Sang-hoon offered a more critical perspective, jokingly noting that since the audience knows the scene so well, they likely realized the roar was a cover-up for the missing dialogue.

From ‘The Glory’ to the Stage: Kim Gun-woo’s Transformation

Kim Gun-woo shifted the conversation toward the physical demands of acting, discussing his role in the hit drama The Glory. Kim detailed the extreme measures he took to embody his character, which included significant weight loss and the use of hair extensions to alter his appearance.

Kim observed a stark difference in how the public perceived him based on his physical state. During his period of extreme weight loss for The Glory, he noted that people were less likely to approach him. Conversely, having recently regained weight, he revealed that he has started receiving offers for “kinder” and more benevolent roles, suggesting a strong correlation between physical presence and casting perceptions in the industry.

Adding a touch of humor to the segment, Kim also commented on the imposing presence of host Kang Ho-dong, naming him as the member of the cast who would be most suited for a villainous role due to his overwhelming aura.

Key Takeaways from the Episode

• Production Focus: The guests are currently promoting the musical Swing Days_Code Name A.
• Professional Rigor: Jung Sang-hoon’s experience with Gummy and Kim Moon-jung underscores the tension between personal style and directorial vision.
• Improvisation: Shin Sung-rok’s “roar” in Jekyll and Hyde illustrates the necessity of quick thinking in live theater.
• Physicality in Acting: Kim Gun-woo’s experience with The Glory highlights how weight and appearance influence casting and public interaction.

For those unfamiliar with the format, Knowing Bros typically places guests in a classroom setting where they interact with the regular cast as “transfer students,” allowing for a mix of structured interviews and spontaneous banter. This episode successfully bridged the gap between the polished image of musical stars and the chaotic reality of their professional journeys.

The three actors continue to perform in Swing Days_Code Name A, bringing the same chemistry seen on the variety show to the theatrical stage.

Check back for further updates on the cast of Swing Days_Code Name A and upcoming broadcast schedules for JTBC’s variety lineup.