Sounds like this will be a comedy from that opening few minutes, doesn't it? This certainly began as lighthearted aside from a brawl Gaurav gets involved with when three toughs try to look at porn on the internet while he's trying to shut up shop for the night, and it appears as if he will be the goofy underdog hero. But soon you begin to twig that all is not right with him and he is actually fixated on Aaryan to the detriment of his sanity, so when he sets off to meet his idol, you just know it will end in tears, though you may not be able to predict precisely how that set of circumstances will play out. All that aside, the real reason to watch Fan was its star, Shah Rukh Khan, King of Bollywood, who gave his acting muscles a heavyweight work out.
For a start, he played Aaryan as a slightly modified version of himself, but gave the character subtle nuances that indicate he may not be worth the adulation that he receives across the globe (this was another mega-budget Bollywood movie that visited locations around the world, like a James Bond effort), a brave element to introduce for such a huge celebrity as Khan. Yet even braver was his depiction of the obsessive fan, who quickly becomes dangerous after a slight to Aaryan from a fellow star (Taher Shabbir) hoping to whip up some publicity for his own nascent career (sort of a variant on the actual star's rivalry with Salman Khan in real life). Gaurav inveigles his way into this upstart's trailer and proceeds to force him with violence to retract his insults and post the results online.
When Aaryan finds out about the reasons behind this public climbdown, he calls the police on his follower and sees to it that he spends a couple of days in the cells, though he does visit him to tell him to back off, and that he doesn't need fanatics like him in his life. All Gaurav wanted was five minutes alone with him to tell him how much he respected, even loved him, but that's all gone to pot, therefore seeing as how he is this man's looky-likey, he sets about ruining his life by behaving badly pretending to be him. In other obsessed fan thrillers (more than one of them called The Fan) the antagonist would turn to murder, but refreshingly Gaurav doesn't go down that route (though he keeps us guessing as to whether he will) as he prefers a more public humiliation for Aaryan who is left picking up the pieces of his reputation.