'Reply 1994' released their 2nd epilogue episode on January 10, detailing NG scenes as well as BTS clips we never got to see in the actual show. One part that became quite a hot topic was of course the beloved Chilbong or Yoo Yun Suk's shirtless scenes as the actor worked hard to make sure his body looked fit enough for the screen. 

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He was shown doing crunches as well as lifts to bring out all the muscles in his arms and abs. The actor hilariously commented while in the middle of being urged on by his trainer, "What am I doing in place of sleeping," with a grimace and a laugh.

It appeared he had nothing to worry about as he lifted his shirt after a while to see if everything looked good. Satisfied with the sculpted abs, he murmured, "It's good, it's good I think," appreciating the results of his efforts before going into shoot for the shirtless scenes.

You can check out the clip for yourself here (around the 15:30 mark).