Depth? Don't expect any. This is about as lightweight (and sometimes silly) as comedy can get, with the usual suspension of disbelief necessary for Bollywood movies.
The title doesn't really have anything to do with the plot; it's more of a programmatic statement, as Mehta tries to intertwine Bollywood and Hollywood elements into a musical romantic comedy.
The Bollywood bits are the more successful, as Mehta sems to have the necessary expertise to exploit them for parody and quirky humour; sadly, the weakest point of the movie is when the Bollywood/Hollywood formula shifts too much towards the Hollywood side and tries to incorporate too much of the typical Hollywood 'romantic comedy' storyline. All of a sudden the script seems to take itself too seriously, and the whole thing, which had been very fresh and entertaining up until then, suddenly tastes very stale, and we get the umpteenth reprise of "love in danger through misunderstanding", and whereas the Bollywood melodrama had been masterly turned into brilliant parody, the Hollywood drama just stands as it is and is presented at face value, which is a major disappointment.
However, the 75 minutes of hilarious Bollywood parody will more than compensate for those 15 minutes of Hollywood lameness. So will the excellent Bollywood-inspired (and Hollywood-compatible) music. Just don't expect depth.