Remember when Kim Kardashian was actually good friends with Paris Hilton?
What about when The Hills were alive with the sounds of laughter between Lauren Conrad and Heidi Montag?
It feels like a very long time ago, doesn't it?
Yes, these and other well known celebrity friendships started out well. Famously, even. But for one reason or another, all took a turn for the worse. Much worse ...
It's sad but true. Not all can pass the test of time.
Or, in the case of Kim and Paris, the test of one friend stealing the other friend's sex tape idea and doing it up even bigger, better and raunchier than the original.
That's basically what led to their falling out, right?
It makes for a good story, in any case. As for what drove Madonna and Gwyneth Paltrow apart? And why Katy Perry isn't returning any phone calls from Rihanna?
Click through the photo gallery above for a reminder of some great celebrity best friends who have turned, at the very least, into celebrity best frenemies...