Odd couple: Justin Bieber and Floyd Mayweather Jr.It seemed like a joke at first, like someone at the Floyd Mayweather Jr.-Miguel Cotto fight party had consumed enough libations to alter his vision and enhance his imagination. But the guy was right: That was pop sensation Justin Bieber marching just behind boxing champion Mayweather toward the ring at the MGM Grand.His wiry body wrapped in two of Mayweather’s five championship belts, Bieber made his way with Team Mayweather, which included rap mogul 50 Cents. Bieber did not flash that 18-year-old smile that makes the girls croon. He played the part, unsmiling, focused.How did this unlikely connection happen? No one is sure. There are thoughts that they connected on Twitter and Mayweather made the young music phenomenon an offer to join him, and Bieber accepted.Bieber and 50 Cents flanked Mayweather as he was announced pre-fight in the ring and Bieber was a vocal supporter from ringside throughout the fight.The real test of if Bieber is part of Mayweather’s circle? If he visits the fighter as he serves an 87-day prison stint for domestic violence and harassment starting June 1.