BTOB's Sungjae talked about his trainee days on KBS 2TV's 'Happy Together 3' and recalled one particular occasion.

He started off saying, "I don't think I went through much hardships. But if I were to mention a difficult time, it would probably be my training period," revealing that it was hard leading such a repetitive live of going back and forth between school, the practice room, and the dorm. So to break away from the dull cycle, he once sneaked off to the movie theater.

SEE ALSO: BTOB celebrates 13th anniversary with 3-day fan concert '3,2,1 GO! MELympic'

He revealed, "However, I just happened to get caught by an agency employee...�I got in trouble like I had done something worthy of death. �I wrote a letter of apology and said sorry. �I even had to get a signature."

He revealed he had to apologize like this to sixty people, surprising the fellow guests and MCs on set and drawing chuckles.�