It was brilliant casting, IMO… There is a point in the film at which Vyjayanthimala’s character, Pushpa, decides to find a new star to cheer up the theater director, Loknath (Balraj Sahni), after he has been mourning the death of his child. (Pushpa herself has just had a child and has ostensibly quit dancing – not that the viewer can possibly believe that, but never mind.) So who could follow up an act like Vyjayanthimala, especially if Padmini isn’t around? The second dance gives you an answer: Kamla Lakshman! (Or Kamala Kumari, as she was billed then.)
The first dance is “Itne Bade Jahan,” with Vyjayanthimala. The second, at about 4:45, is “Hai Tu Hi Gaya Muhe Buhl” with Kamala Lakshman. (For some reason, both get Lata Mangeshkar’s voice.) Then, at the very end, there’s a brief superimposed glimpse of Vyjayanthimala doing “Bum Bum Bum Baje Dumro,” a dance that I posted back on her birthday, which is also screen capped in the present image header.