Karan will be seen as a rich businessman who plays a crucial role in Ranbir Kapoor's life in the film, with shades of grey.
"It was great to be directed by Anurag. My work was mostly with Ranbir Kapoor... So he is my favourite co-star and my director Anurag, Phantom Films and Fox Star Studio... thankful... I don't have choice," Karan said at the wrap up party of 'Bombay Velvet' held last night here.
Karan's first movie appearance was over a decade-and-half ago in the Shah Rukh Khan-Kajol-starrer 'Dilwale Dulhania Le Jayenge'. Then he did cameos in 'Om Shanti Om', 'Luck By Chance' and Kal Ho Na Ho among others.
Present at the party were Vijay Singh, Anurag Kashyap, Vikas Bahl, Karan Johar, Ranbir Kapoor, Vikramaditya Motwane and others.
Set against the backdrop of love, greed, violence and Jazz, 'Bombay Velvet', first in a planned trilogy, tells the story of how Bombay became a Metropolis. Historian Gyan Prakash's book 'Mumbai Fables' forms the basis for the movie.
"It is a love story... Beyond this I cannot tell you anything. We will release the first look in October," the director said.