UFC fighter Casey O'Neill is shouting out Olympian Rachael "Raygun" Gunn -- after a UFC 305 victory she busted out the Aussie's breakdance ... but it was way more mocking than tribute.
Casey defeated Luana Santos by a unanimous decision at UFC 305, which was held in Perth, Australia -- so, naturally, the Aussie fighter had to celebrate with an impersonation of her countrywoman .