The scene where Johnny Lever demonstrates different kinds of laughter and makes fun of Shah Rukh Khan while Hrithik Roshan stands next to him, smiling, is an insider joke referring to the Coke wars the two stars had with each other. Hrithik supported Coke, Shahrukh Pepsi. A Pepsi commercial made fun of Hrithik, which created quite some outrage among his fans and was widely reported in the media.
The film was set to be a artistic film. But Khalid Mohammed decided to commercialize the film due to pressure from the distributors. Karishma Kapoor had a dance number added. Johnny Lever park scene was added. More songs were added. Hrithik's role increased including his work out and more songs.
The shots on the highway and before the bill board in the song "Aaja Mahiya" were done while regular traffic was going on. This would no longer be possible now, since Kaho Naa... Pyaar Hai (2000) has been released, since whenever Hrithik Roshan appears in public, traffic stops and people surround him by the hundreds.
Originally Hrithik Roshan had a very small role. But after Kaho Na Pyar Hain became a blockbuster over night, Khalid Mohammed panicked. He knew expectations were high because of Hrithik, so he increased his role. Many scenes like his workout, a extra song and many scenes were added to suit Hrithk's new status of a Superstar.
Fiza - Tu Fiza Hai antras were made into "Sun-e-Mere Dil" from Paap (2003). Also the tune for Tu Fiza Hai has been in countless Anu Malik songs in the 80s, and some in early 90s, notably "Kitabein Bahut Si" from Baazigar (1993) and "Aap Ka Chehra" from Talhalka.