Katy Perry showed up for the Miley Cyrus gig in Los Angeles on Saturday night ... and Miley called her up to the edge of the stage for a lip lock.

Ironically, it seemed to be Katy who was a little uncomfortable with the girl-on-girl kiss. It looked like Miley was trying to bury some tongue in Katy's mouth, but Katy pulled away. (Here's video.)

In related news, Miley is now orally pleasing Abe Lincoln as opposed to Bill Clinton ... and Miley is doing a HORRIBLE country version of Outkast's "Hey Ya".

Katy Perry walked the runway at a fashion show in Milan, Italy this past Thursday ... and was BOOED by photographers after she told them, quote, "You're all going to get your picture, so shut the [eff] up."  (Here's video.  WARNING!!!  Profanity.)

Just 24 hours later, Katy arrived at the Los Angeles airport and was booed AGAIN, when she wouldn't talk to reporters about being booed in Milan.  (Here's that video.  WARNING!!!  At the end of the clip, Katy's assistant shoves a guy and drops an F-bomb.)