2PM's Junsu was caught in the act of singing along to T-ara's Bo Peep Bo Peep during the girl group's performance on Music Core this weekend. The mysterious voice was revealed when 2PM's Taecyeon and 2AM's Seulong posted messages on their CyWorld pages. Junsu wrote back to Taecyeon, "Ah, you little loud mouth." To Seulong, he wrote, "Ah, I'm so embarrassed." It was reported that Junsu went to T-ara's dressing room, backstage at Inkigayo today and apologized. T-ara replied, "Because of Junsu, "Bo Peep Bo Peep" became more known. Even though it was an accident, we are thankful for it." That wasn't the first time 2PM and T-ara "came together." 2PM also did T-ara's Bo Peep Bo Peep dance a few of times and T-ara returned the favor by doing a Heartbeat dance in the middle of their performance, rousing theories that the two groups are cross-promoting. Now that 2PM has six members, maybe some T-PM action would be good eye candy. They already seem to have gotten close.