Genelia as Tsukushi? I would never have thought of that but it makes so much sense! I think I'd make Shahid as Ruii though; as adorable as Imran is I don't think he's that good an actor. I've not seen Siddarth in anything so I'll have to take your word for it. But I think if I had to choose I'd want Ranbir as Domiyuji - he's dorky enough to pull crazy!Domiyuji. :)

And for Shirgeru I instantly thought of Deepika Padukone. I don't know why, she just popped into my head.