The stars of�JYP Entertainment delivered an explosive first collaboration concert on December 24th. Fans naturally expected�Park Jin Young, the�Wonder Girls, J-Lim, 2PM, miss A, JOO, and�San-E, but they were left gasping for air when former JYPE artists�Rain, Son Ho Young, and Kim Tae Woo all made their cameo appearances throughout the concert. From blurry group photos to cute selcas (before and after the show), fans were given a sneak peek into what went down backstage. Already hyped for their concert, the atmosphere backstage sparked into a wildfire of congratulations and well-wishes, as San-E celebrated his�100th day since his debut. One JYP Nation member even took an interesting photo with him, but concealed his identity by wearing a mask. Can you guess who it is? Check out the photos below! [gallery]