The film was first being made in the late 50's by Guru Dutt. The original film starred Kishore Kumar and Waheeda Rehman. In the olden days, every film maker had to show the censor board their films after three reels. This was done to avoid confrontation with censors later on. After shooting 2 reels, Guru Dutt submitted the film to the censor board. After viewing the film, they rejected the theme.They felt the story line of a lady teacher and her student niece falling in love with the same senior professor was in poor taste.Guru Dutt decided to shelve the film.
Writer Abrar Alvi hated the old lady's character. He wanted it removed from the script, but Lekh Tandon wanted the character to remain in the film. They eventually changed the script to Shammi Kapoor falling in love with a outsider rather then a student.
Dev Anand and Raj Kapoor rejected the lead role.
Shammi Kapoor insisted Nasir Hussein or Shakti Samanta to direct the film. But Lekh Tandon would not sell his script. Shammi Kapoor then made up a clause in the contract. If after 3 reels he did not like the Lekh's work, he could replace Lekh Tandon with a director of his choice. Shammi was hell bent on replacing Lekh Tandon. During a trial with distributors, everything changed. The distributors were so happy with the film they bought all the territory distribution rights. This made Shammi Kapoor embrace Lekh Tandon and realize Lekh Tandon was best for the job not anyone else.
The story doing the rounds was that Shammi Kapoor and Feroz Khan had a brutal bloody fight in the mid 60's at the Shalimar Hotel over actress Kalpana. Both were involved with her. Years later another story surfaced of Shammi Kapoor and Feroz Khan fighting at the Bobby party in 1972/73.