That was because initially, the film was meant to be an English film, and the story was a love story between an Indian girl and an American boy who meet in Europe. But later, it was decided that, the same story would be made in Hindi, and Shah Rukh Khan was cast as the hero.
Also, In the last scene of the song, Ruk ja, Shah Rukh drops Kajol on the floor. Remember?
Shah Rukh and director Adi Chopra had not told Kajol about this shot, so that they could capture a genuine reaction from her. Kajols shocked expression was a real one in the movie, and she claims she got hurt when she was dropped. She was angry for a while and refused to speak to them, but they patched up within a day.
"Ho Gaya Hai Tujhko To"