The classical song Pag Ghungroo Bandhe Meera Nache sung by Kishore Kumar had a part of classical lyrics (Sa Sa Sa Re Ga Re Ga Pani Ni Sa Sa Sa) this particular verse was sung by classical singer P Satyanarayan Mishra.
Amitabh was facing a heroine crisis in the early 80's. He had stopped signing films with Rekha. Raakhee was transitioning to more mature roles. Parveen was in and out due to her illness. Neetu was retiring. He would not act with Moushumi - either due to ego hassles or personality clashes. Same with Shabana. Or he did not consider them A-Grade. After working with Smita in Shakti Amitabh requested Prakash Mehra to sign her for Namak Halal as well. That was also his way of making up for getting her replaced by Jaya Bhaduri in Silsila.
The "I can talk English scene" was mainly improvised, and it was shot with the director Prakash Mehra outside the room, a condition Amitabh Bachchan set as he would start laughing otherwise.
Smita Patil was so upset after shooting Aaj Rapat Jaye . She locked up herself in her room and cried for hours. Smita did not want to be a commercial actress and did not want to sing and dance. Even while shooting the song she was very upset and it was Amitabh who put her at a little ease.
When the film was launched in 1978 Vinod Khanna was doing Shashi Kapoor's role. Vinod opted out due to problems with Prakash Mehra.