Welcome to our weekly Twitter Roundup, where we take the funniest, most popular, wierdest, or most profound celebrity tweets, and put them in one place for you. This week we have Bieber on tour, Lambert bashing bullies,  Rihanna undressing for the camera and more.

Biebs is on his way to Nashville - and his fans can't wait. 15K+ RTs

Shakira, Gerard Pique and soon-to-be-born child use their popularity to support UNICEF. 5K+ RTs

Steve Martin being...Steve Martin. 800+ RTs

Justin Timberlake celebrates newest single's hit success. 3K+ RTs

Anthony Bourdain suffers through a crappy flight. 400+ RTs

Rihanna shows she's 'complex' 1.5K+ RTs

LiLo pulls a Twitter Kanye. 400+ RTs

And finally, Adam Lambert puts his foot down on bullying. 600+ RTs

That's it this week folks! Check back next Friday for next week's Twitter Round Up