Ideally, it would have been fabulous to have Shah Rukh Khan play Surinder Sahni all the way. But Raj being Raj had to somehow squeeze himself into the proceedings. It's not the same though, because Raj isn't iconic any more, he is Suri's interpretation.
To his credit, Shah Rukh Khan plays both the dissimilarity and connection with the flamboyance of Raj and earnestness of Suri. Rab Ne Bana Di Jodi works primarily because of SRK's simplicity rendered to the latter. Moreover, despite the implausible premise, he has us convinced and routing for him. A-one, hai ji? You bet!
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