On today's KBS 2TV's 'Happy Together 3,' Kim Gu Ra's son, Donghyun, also known as MC GREE, made an appearance!

In a phone conversation with his father, however, Donghyun probably face palmed because his father dropped the bomb, "Donghyun has a girlfriend one year older than him," revealing they've been dating for 100 days.  After they hung up, Yoo Jae Suk and Park Myung Soo said worriedly, "Will you be okay?"

SEE ALSO: Dita, Jinny, and Minji announce departure from SECRET NUMBER following contract termination

Zico added to this with, "There's a picture of Donghyun's girlfriend in his phone messenger. Next to it, it says, 'Love you,'" raising eyebrows.

Jun Hyun Moo then mentioned Kim Yoo Jung, whom Donghyun had chosen as his ideal type, asking, "Is she similar?" and Donghyun replied, "She's different.  I picked Kim Yoo Jung out of three [choices]; she's not my ideal type.  My girlfriend is my ideal type."

Shin Dong Woo added, "He always lets her listen to his songs.  One day, he played a song for me, so I asked him, 'What kind of song is this?' and he replied, 'I'm going to play it for my girlfriend.'"