It looks like Justin Bieber hangs with a tough crowd. The impressionable teen made a very public appearance by the side of fighter Floyd Mayweather before the boxer's highly anticipated match against Miguel Cotto. The 18-year-old "Never Say Never" singer, along with rapper 50 Cent, walked in with Mayweather's championship belts. Another member of Mayweather's crew, Lil Wayne, was also ringside. Mayweather...50 Cent...Lil Wayne... Justin Bieber... One of these things is not like the others. Many fans of the squeaky-clean singer were surprised to see him hanging with the noted band of thugs, all of whom have well-documented arrest records. Mayweather himself starts a jail sentence for domestic violence on June 1. According to TMZ, the 35-year-old boxer is a Belieber who has taken the "Boyfriend" crooner under his wing. Despite being found guilty of pounding on his girlfriend, Bieber thinks that his "mentor" is "misunderstood." Mayweather apparently approached Bieber around four months ago and invited him to be a part of his posse. The two first connected after Mayweather watched Bieber's bio Never Say Never and reached out to Bieber's peeps. Insiders say Mayweather wanted to mentor the singer, who also happens to be a die-hard boxing fan. Bieber sees Mayweather as a "hard-working and clean-cut guy."