This week's Twitpic of the week involves Justin Bieber and one man you definitely don't want to mess with. The 'Never Say Never' singer jokingly tweeted about trading punches with Brazilian mixed martial artist and UFC Middleweight Champion Anderson Silva along with a picture of him and Silva. Can you imagine Justin Bieber fighting Anderson "The Spider" Silva?! We're almost 100% positive that is a horrible, horrible idea, Justin. Bieber jested, "ok its on!! the fight has been vs @spideranderson - I am NOT the heavy favorite. haha. #gooddude."

Also, 50 cent was back at the dentist again! The poor guy has had more dental work these past few weeks than most people will have in a year! Feel better, Fiddy. Other memorable TwitPics include Ciara's super glam look that she rocked at a Valentino runway show, some 'Glee' cast members hanging out together, Jessie J being silly at lunch, and Swizz Beatz getting his daily dose of veggies with a V8 juice.

What do you think? Who deserves the win for best TwitPic of this week? Scroll through the gallery above and leave us a comment below.