In Santoshi's Ajab Prem Ki Ghazab Kahani Ranbir plays the melancholy lover-boy hopelessly in love with the idea of being in love. The character was immortalized by Raj Kapoor in Mera Naam Joker and before him, Chaplin in City Lights. Ranbir in Ajab Prem Ki Ghazab Kahani plays 'Prem' a true inheritor of the two imperishable heroes from the past. Says Santoshi, "I decided Ranbir was the right actor for my film from the time I saw Saawariya. He plays Prem an innocent guy with a heart of gold. Yes there will be distinct elements of Charlie Chaplin and Raj Kapoor, though not too much of it. Raj Saab has already done it all in Sri 420 and it would look repetitive. Also, that level of political and sexual innocence would look odd in present times. Let's say Ranbir plays the Charlie Chaplin and Raj Kapoor of our times."
Santoshi fondly recalls the experience of working with Ranbir's father. "In my film Damini, Rishi Kapoor played a really difficult role...of a man caught between his duties towards his family and society. Though Rishi didn't have an author-backed role in Damini, what a beautiful job he did."
Ranbir on the other hand not only has the title role in Ajab Prem Ki Ghazab Kahani. His character also gets to go through a series of life-changing experiences. "Ranbir takes interest in every aspect of the film. He's a keen student if cinema. His enthusiasm for cinema goes much beyond his role. I know I'll enjoy my shooting with him. But beyond that I'm right now enjoying interacting with him," adds Santoshi. In the next two months, Santoshi will be doing a first-look photo session between Ranbir and Katrina Kaif. "We'll also be sitting on the costumes because the clothes are a very important part of the story. We start shooting the film only when Ranbir returns from his long foreign schedule of the Yash Raj Films," informs Santoshi.
Being a full-on love story Pritam is doing the music score of Ajab Prem Ki Ghazab Kahani. "I've been watching Pritam's growth as a musician. And I can't think of anyone else for this project," says Santoshi who has earlier worked with the likes of A R Rahman.