VIDEO+PHOTOS: Lady Gaga surprises fans at Elton John's free concert

Lady Gaga joins the legendary singer and her long-time friend Elton John onstage during a performance of Elton's 1974 hit "Don't Let the Sun Go Down on Me" at his free concert at the Tower Records in West Hollywood, CA. The concert which was streamed live on AOL.com, was organized to thank the City of West Holloywood for their support of the Elton John AIDS Foundation. Gaga and Elton are well-known music stars who are active in supporting LGBT community and fighting against HIV/AIDS. Below is the video of their performance.

In case you don't know, Lady Gaga is set to attend and perform at the 88th Academy Awards today! Live Stream is available here.

Lady Gaga arriving at the Tower Records

Lady Gaga leaving the Tower Records