During the filming of the song ‘Ho Gaya Hai Tujhko Toh Pyar Sajna’, Shah Rukh told Karan Johar to start directing films. He also promised that he will star in Karan’s directorial debut. When Kajol got to know about this conversation, she hopped on the next movie train as well. That’s how Kuch Kuch Hota Hai happened.