It all started Monday on Australia's "Sunrise" program, when one of the hosts riffed off Perry's hit "I Kissed a Girl" to lead into a discussion of the "Roar" singer's recent lip-lock with Cyrus during one of the "Wrecking Ball" singer's shows.
"Scandalous!" Perry joked, before explaining what went down.
"I went to her show, which was amazing. It is very colorful — I mean that in all ways. She has this one part where it's like a kiss cam. I just walked up to her to give her like a friendly girly kiss, you know, as girls do. Then she like tried to move her head and go deeper and I pulled away.
"God knows where that tongue has been," Perry declared. "We don't know. That tongue is so infamous!"
Well, we know it's been on myriad red carpets, in paparazzi photos, on TV, in concert ...
On the show, Perry acted as if Cyrus were a pal, but whatever translation made it Cyrus' way a couple of days later did not please the tongue's owner one bit.
And so a feud was born.
"Girl if ur worried abt where tongues have been good thing ur ex boo is ur EX BOO cause we ALL know where THAT [tongue] been," Cyrus tweeted Thursday, attaching screen grabs of Perry doing her Aussie interview.
Now, whether she's referring to recent ex John Mayer or ex-husband
So was Perry really grossed out, or was she just having fun in the moment on TV? Check out the video above and decide for yourself if Cyrus was overreacting or right on target when she lashed out.
Die-hard Perry fans can watch her take over the entire Monday "Sunrise" program; those less devoted can catch the Miley moment starting around the 24:40 mark. There's also a pretty funny bit at the end where Perry does the show's weather forecast — mangling the geography of Australia rather badly.
[Updated, 3:50 p.m. March 6: Looks as if the ladies are speaking to each other. After Cyrus posted an illustration of the smooch Thursday on Twitter with the message, "Dontchyouuuu act like you didn't lurvvvvv it @katyperry," Perry promptly tweeted back her intentions: "Oooo gurrrl I'm gonna give you the BIGGEST spanking when I see you in the UK bb!" Kissing, spanking, it's all good ...]