Yun Toh Humne Lakh Haseen Dekhe Hain- The Game Changer for Shammi Kapoor

This song and the film'Tumsa Nahin Dekha' was a gamechanger for Shammi Kapoor. Before this film, he had given 18 flop films in a row. This film was written by Nasir Hussain in keeping Dev Anand in mind. When Dev Anand refused to do this film, Shammi Kapoor was given this film.
This superhit song was written by Sahir Ludhianvi and composed by O P Nayyar well in advance keeping in mind Dev Anand. This was the only song written by Sahir in this film, he also opted out of the film because Dev Anand is not doing the film. Those days only Dev Anand had a flamboyant image and his earlier films (Munimji and Paying Guest)  with the producers had similar roles and were superhit.
The director of the film Nasir Hussain said in an interview that he was reluctant to take Shammi Kapoor as his hero for this film, it was his first film as a director and he wanted to work with an established hero. S Mukkharjee the producer suggested the name of Sunil Dutt after Dev Anand's refusal, ultimately the name of Shammi Kapoor emerged. 
Shammi Kapoor, who knew the story of the film and also knew that it will be a musical Rom-Com was desperate to grab this film to boost his sinking career. Nasir Hussain thought of changing the earlier image of Shammi Kapoor, asked him to remove his mustaches and change his hairstyle.
Shammi Kapoor told in an interview that this film was his dream film, he wanted this type of a role to show to the world his style. Those days no specialized choreographers were available for the songs. Heroes used to be sober or simpler in their songs. I had a great sense of dance and music, could improvise my own steps. So I asked Nasir Hussain to give him the recording of the song so that he could prepare for the song.
The day he got the recording of this song he went up to the terrace of his house at Chembur, he danced with the rhythm throughout the night., until every line, every beat had seeped into his body.
When the song was being picturized, Nasir Hussain gave him the full freedom to make his moves and steps. Everybody present there were surprised to see Shammi performing the song. Nasir Hussain was happy, he wanted Shammi Kapoor to do differently and he did it.
This is a version song, the other version was sung by Asha Bhonsle, the favorite of composer O P Nayyar.

Song of Tumsa Nahin Dekha 1957 (Both Versions)