Celebrities took to Twitter  this week to share photos from their birthdays, travels, and behind-the-scenes fun. Aziz Ansari joked with Jay-Z  and Beyonce backstage at Bonnaroo, while Dax Shepard did his best to fit in while on a trip to Italy. Cory Monteith  was surrounded by lovely ladies, and Julianne Hough blew out her birthday candle for the camera. Click through to see all the shots, and don't forget to follow us on Twitter  for exciting news and exclusive photos!
The Real Thing
Justin Bieber was so happy  to reunite with Kim Kardashian  but warned her about his enthusiastic fans.
Donnie Wahlberg joined fellow Bostonians like Dane Cook  and Maria Menounos to cheer on the Celtics .
Pomp and Circumstance
Alicia Keys  brought out her fiance, Swizz Beatz, while performing at the World Cup  opening ceremony.
Up in the Cub
John Legend  met new furry friends in South Africa  with his girlfriend, Chrissy Teigen.
Peter Facinelli  bonded with his onscreen wife , Elizabeth Reaser, during his weekend of press duties.
Tom Hanks  celebrated Julia Roberts's last day  on set in LA.
Cory Monteith  was surrounded by ladies like Leighton Meester, Katie Cassidy, and Selena Gomez .
Playing Dress Up
Adrianne Curry can't resist a costume .
Ashley Greene  tried out her new Mark cosmetics .
Lauren Conrad  joked around with friends  on set.
Hours of Fun
Taylor Swift  showed off the bracelets her fans gave her  during a 14.5-hour autograph signing.
Stuck in the Middle
Aziz Ansari found himself between Beyonce and Jay-Z  at Bonnaroo.
Nicky Hilton  had a late night in Las Vegas  with sister Paris.
Martha Stewart  showed off a new hat .
With the Band
Conan O'Brien  checked out a famous guitar store  in Nashville.
Justin Bieber didn't mind letting Kim Kardashian  mess up his hair .
Make a Wish
Julianne Hough blew out the candle on her 28th birthday .
When in Rome
Dax Shepard tried to blend in  with the locals on his trip to Rome.
Live in Five
Lea Michele  made an appearance on Regis and Kelly  with Regis's wife, Joy.
Kellie Pickler and Sheryl Crow  crashed David Spade's photo  with Kid Rock .
Nina Dobrev  thinks Amanda Seyfried's dog  is the coolest.
Need For Speed
Ashton Kutcher  took his shiny red car  for a spin.
Lake Bell put on her hard hat  to volunteer.
Lindsay Lohan  indulged in a True Blood-themed Carvel cake .
Donald Faison started a workout routine and declared war against buff Zac Efron .