Zach Galifianakis is using his fame for the greater good. Former homeless woman Mimi Haist, 87, who reportedly has been a friend the “Hangover Part III” star for almost 20 years, will be joining him as his date on the red carpet for the premiere of the third and final installment of the summer blockbuster hit film series, also starring Bradley Cooper, according to Coleman-Rayner photo agency.