Tim Sylvia and Andrei Arlvoski fought each other 4 times in their career, including a trilogy in the UFC that had the heavyweight championship switching hands between them. At one point, the rivalry became so personal it even involved a girlfriend that allegedly went from Arlovski to Sylvia.
For those who don't know, this even led to the classic 'How's taste my pee pee?' line from Arlovski, which became somewhat of a meme in MMA, and is still referenced on one of BE's more popular features.
Fast forward to 2015, and now the two former champions are seen hanging out at a UFC event.