Ellen DeGeneres joined Taylor Swift on stage during her sold-out Speak Now tour show at Staples Center in Los Angeles.
When she walked on stage, she looked at Taylor and said: "I was looking for the ladies room. I'm so sorry."
Taylor said: "This has been happening quite a bit. People are just going about their daily lives and they end up on our stage."
Ellen hung out with Taylor as she sang "Our Song". The segment will air on "The Ellen DeGeneres Show" September 14th as part of Ellen's Season 9 premiere week.