'Summertime Ball'

Singers Nicole Scherzinger performs with Enrique Iglesias perform during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Singer Nicole Scherzinger performs during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Jennifer Lopez performs during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Jessie J performs during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Nicole Scherzinger performs during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Singers Nicole Scherzinger and Enrique Iglesias perform during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Singer Jennifer Lopez is seen backstage during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Nicole Scherzinger performs during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Far East Movement perform during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Singer Jennifer Lopez performs during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)

Singer Cee Lo Green performs during the Summertime Ball at Wembley Stadium in London on June 12, 2011. (AP/Yui Mok)