News Justin Bieber Sang 'Happy Birthday' to Himself By Rosalyn Oshmyansky 3:15 PM PDT, March 15, 2015 Instagram "Happy Birthday to You" is usually how the song starts out, but for Justin Bieber, it went a little different.The singer turned 21 on March 1, and on Saturday after filming the Comedy Central Roast in his honor, he jetted to Las Vegas to celebrate his birthday at OMNIA Nightclub in Caesars Palace.Bieber jumped on the DJ booth to show off his dance moves before he sang himself a birthday tune.PHOTOS: Justin Bieber's 21st Birthday"Happy Birthday to me, Happy Birthday to me, Happy Birthday to me," he sang."Happy Birthday" was not the only song on his list as he also sang his track "Wait for A Minute."As for his cake, he had a replica of a 1965 Lincoln Continental, a recent birthday present.Bieber reportedly joked with guests as he swapped the "21" emblems and changed his age to "12."He had so much fun that he tweeted out, "Tonight was one of the best nights ever. Thank you to everyone involved. Thank you."Tonight was one of the best nights ever. Thank you to everyone involved. Thank you— Justin Bieber (@justinbieber) March 15, 2015Check out the video below to find out 6 things we learned from Justin Bieber's recent Men's Health interview.6 Things We Learned From Justin Bieber's Men's Health Magazine Interview Related GalleryWhat Happened in Vegas?