Britney Spears' 2011 Wango Tango

Stepping out for her guest co-host duties, Britney Spears was busy entertaining the audience at Staples Center in Los Angeles, California on Saturday night (May 14).

The "Hold It Against Me" singer teamed up with Ryan Seacrest to kick of KIIS FM's 2011 Wango Tango Concert - with the show's lineup including Selena Gomez, Ke$ha and Jennifer Lopez.

Tweeting about the busy day's plans, Brit wrote to her millions of followers, "Rehearsals all morning. Wango Tango all night.... -Britney"

Meanwhile, Miss Spears also recently tweeted her choice of "I Wanna Go" as the next single to be released from her Femme Fatale album, as she posted the following message: "So excited 2 announce that the fan favorite #IWannaGo is my next single from Femme Fatale! Shhh, it's my fav too!"