AceShowbiz -

Jennifer Hudson didn't expect that she would come as a guest performer at Keith Sweat's recent concert. The singer, who attended the show with her husband David Otunga, joined the veteran R&B crooner onstage for an impromptu duet.

Hudson and Sweat excited the crowd at Los Angeles' Nokia Theatre with a live rendition of the latter's classic titled "Nobody". Despite not knowing all the lyrics of the song, the "American Idol" alum still gave an amazing performance. "OMG @OGKeithSweat just surprised the hell out of us @davidotunga at his concert tonight. We Will never forget it!! Only my life wow!!!" Hudson tweeted after the show.

The 32-year-old singer is currently readying a new song called "Walk It Off", which was produced by Timbaland. The track will appear in her next LP, which is expected to be released later this year via Sony Music Entertainment/RCA Records.

In other news, Hudson has just been added to the line-up of performers at the upcoming We Day U.K. charity event at London's Wembley Arena on March 7. She joins other performers that include rapper Dizzee Rascal, "Harry Potter and the Order of the Phoenix" actress Evanna Lynch, "Glee" star Jacob Artist and British singer Birdy.

"We Day captures the very spirit that my sister and I continue to spread within our own organization, the Julian D King Gift Foundation," Hudson has commented on the event. "It's that inspiration of the next generation that will bring change to this world. I've been a part of We Day in North America and the energy from these young people who come together to make a difference is simply contagious."