Jaime Foxx was a comedian long before he won an Oscar or released a CD. That being said, it shouldn't have been a surprise that he'd "crack jokes" all night, while at an event. It seems as though Rihanna, however, couldn't take a joke, while partying with Jay-Z in Vegas, for a July 4th celebration.
Foxx, supposedly, got onstage and pleaded for Rihanna to join him. As she refused, Foxx begged the DJ to play Rihanna's Grammy-winning hit, "Umbrella." This didn't seem to help matters, as Rihanna aimed for the exit. Still "cracking jokes," Foxx pleaded for Rihanna to stay and asked that the DJ to stop the record.
Rihanna returned to the party and "enjoyed herself," but reports noted Rihanna as "furious" for the duration of the night.