Ajith and Shah Rukh Khan have been friends ever since they worked together in Asoka which SRK also produced. Later both took up the same role with SRK remaking Amitabh Bachchan's Don and Ajith doing Rajinikanth's Billa. Currently SRK is all set to release Don - 2 while Ajith is working on a prequel to Billa.
SRK has always been an admirer of Ajith and he speaks most warmly of him. The Baadshah of Bollywood was apparently inspired by Ajith's look in Paramasivan (The matted locks pulled back and tied up) and has adapted it for Don - 2.