On yesterday's episode of "Music Bank", Kim Tae Woo collaborated with Wheesung for a special rap performance of "Words That Freeze My Heart". Hilariously, a live broadcast mistake resulted from the collaboration, as Wheesung burst out into laughter after watching Kim Tae Woo stumble with his rap. Being a vocalist, Kim Tae Woo was unable to keep up with the pace and so he stumbled over his words. Through K-Will's Twitter, Wheesung later apologized for laughing. "I'll be saying this in place of Wheesung since he doesn't have a Twitter. We would like to apologize to everyone for failing to train our bear!" Meanwhile, on his mini-homepage, Kim Tae Woo wrote, "Bear Tae Woo tried to rap for the first time in 12 years in order to help out my friend Wheesung. Unfortunately, it was a fail. But still Wheesung, don't you think that you laughed too hard~? I mustered the bravery to rap for you. I'm sorry and I love you, my friend. Wheesung forever!" Netizens commented, "I laughed along with him", "This wasn't Music Bank, it was Gag Bank", "Wheesung is a person too, he has to laugh if it's funny", and "Wheesung's known to be a professional, so imagine how funny it was." -- Check it out below! (Starts around 2:20) Source: Newsen via Nate, Sports Chosun via Nate, OSEN via Nate