Katy Perry and Adele have ruled the charts this past year, so it's not surprising that Katy chose to pay tribute to her fellow hitmaker while performing in the UK earlier this week.

During her performance in Sheffield, England, Katy was singing an acoustic version of her latest single, "The One that Got Away," when, in the middle of the song, she broke out into a chorus of Adele's #1 hit "Someone Like You," which has a similar theme.  The excited audience sang along with every word, and then Katy went back and finished singing "The One that Got Away."

By the way, if Katy's song "The One that Got Away" reaches #1 on the Billboard Hot 100, she'll be the first artist in history ever to score six number-one hits from a single album, in this case Teenage Dream.