Unless you've been living under a rock for the last four years, you'll no doubt be aware that Katy Perry and Taylor Swift are not exactly on the best of terms.
The chart-topping pop stars have tended to shy away from naming each other in the press since falling out in 2014, but that's just made their cryptic social media messages, music video swipes and occasional shady remarks that's made their feud all the more intriguing.
The bad blood showed no sign of ending on American Idol last night (March 19), when Katy Perry used some very choice words to describe her former friend.
During one of the auditions, 33-year-old Perry, who is currently serving as a judge on the reality singing competition, came face to face with a self-porfessed Taylor Swift fan - and managed to throw some artful shade her rival's way.
Asked what musician he looked up to, the contestant answered: "I'm sorry for this Katy: Taylor Swift."
"Oh, you don't have to be sorry," Perry replied.
"I love Taylor Swift," he added.
"I love her... as a songwriter... as well," Perry responded pointedly, before giving a shrug.
Oof. Sometimes, less really is more.
Katy and Taylor's public falling out dates back to 2014, when Swift revealed that her diss track 'Bad Blood' was about a fellow female pop star who had "tried to sabotage" her arena tour.
The incident led to Katy - who had hired several dancers working on Taylor's Red Tour for her own Prismatic World Tour - labelling Swift a "Regina George in sheep's clothing"; a reference to the bitchy Queen Bee of 2004 teen comedy Mean Girls.
Perry also tweeted a cryptic message describing time as the "ultimate truth teller" - a message the 'Swish Swish' singer pointedly retweeted after Calvin Harris accused Swift of trying to "bury" him "like Katy" after their break-up in 2016.
Watch Katy's oh-so-graceful shade on American Idol below: