Tuesday, February 8, was a day made in tween and reality show heaven, with events revolving around Justin Bieber and the Kardashian sisters. At Barnes and Noble in Santa Monica, Khloe and Kourtney Kardashian signed copies of their new book Kardashian Konfidential, which chronicles the lives of the famous sisters growing up and offers advice and guidance to tween girls. Across town an even bigger event unfolded, as excited LA tweens and tween idols--including Kardashian half-sisters Kendall and Kylie Jenner--flocked to the premiere of Justin Bieber: Never Say Never at the Nokia Theater LA Live. Bieber was greeted by screaming fans and walked the red carpet alongside Miley Cyrus, Selena Gomez, Usher, Will.i.am, and reality show star Whitney Port. Check out photos of the events below!