The MMA/pro wrestling crossover has been alive for decades, before mixed martial arts really even existed. From Billy Robinson transitioning his fantastic catch-as-catch-can wrestling ability into the AWA, all the way to Bobby Lashley taking his professional and amateur wrestling to WWE and TNA wrestling, the crossover is still alive. While the UFC isn't as quick to embrace former WWE stars these days, that wasn't always the case. Since the company's inception all the way through their mainstream explosion, pro wrestling stars were instrumental in gaining attention for the UFC. It just so happens that a few wrestlers happened to become champions, greats, and even UFC Hall of Famers. Some names you'll know, others you wont, and some will flat out surprise you. This may not be the last of this list, either, as rumors have been flying about UFC Women's Bantamweight champion Ronda Rousey and her teammates-- known as the "Four Horsewomen"-- making a WWE related appearance this summer. Let's take a look at five WWE superstars that tried their luck within the confines of UFC's octagon.