"Ae Kash Ke Hum" is one of my favorite musical sequences ever. it is so beautifully realized, with Kumar Sanu's voice and Shah Rukh Khan's endearing performance. In the entire number, Sunil is the only one singing. It is one of the only songs in the film that is entirely "within" his head. In other non-diagetic songs in the film (deewana dil deewana, aana mere pyar ko, woh toh hai albela), the side characters are joining in, or leading the musical number. but Ae Kash Ke Hum only has Sunil singing--and technically, he only sings on screen for a brief sequence.
It takes place after Sunil points out a shooting star to Ana.
And while the star is reflected in her eyes, he looks over to her, and the camera does a sort-of match cut from the shooting star to the moon, and an overhead light at the fair.
The camera pans down, and we see the empty carnival, with only Sunil and Ana, both dressed in white, romantic, filmy outfits, while they waltz across the empty concrete. It is only in this imagined version of reality that we see Sunil actually mouthing along with the words of the song.
We exit that dream sequence back into reality--Ana is trying to make playful, platonic conversation while they waltz among other couples. Her conversation falls on deaf ears, however, as he continues to stare at her dreamily. We don't hear her words, we don't here what she's saying. We continue to hear "Ae kash ke hum hosh mein ab aana na paaye." (trans. "I hope that I never regain my consciousness").
It's such a perfect encapsulation of Sunil as a character. And is a perfect example of what musical numbers can do that films driven only by dialogue can't. Music is a reflection of a character's heart: their emotions and thoughts that they cannot speak outside for whatever reason. But for a character like Sunil, who wears his expressions so clearly and openly on his face, music isn't some hidden thing. It comes easily to him, it is at the forefront of his mind. It is screaming from within him, underlaying the scene as he loses himself in the cotton candy fantasy he has built for himself and Ana, only for it to all melt away at the end as his lies are revealed, and Chris and Ana walk away together.
In conclusion, they don't make lover boys like they used to, and they will never make a lover boy like Shah Rukh Khan again.