G.One is always shown with blue eyes. But just before the song "Chammak Challo" he has brown eyes that will change back into blue ones as he starts singing.
In the movie, Karva Chauth is shown before Dussera, but in actual, Dussera comes 10 days prior to Karva Chauth.
In the train sequence, the train travels from Bandra to CST. This is the harbor line route of the Mumbai locals. None of these harbor line trains have 12 coaches, while the train in the movie had 12 coaches.
In the song "Criminal", the girl wearing the panty has "Crimnal" written on it, without an "i". Later in the song, on the same girl's panty, the mistake is corrected & now the panty has "Criminal" written on it, with an "i".
During the train sequence, the train is first shown crossing Bandra station. Then it is mentioned that the train crosses Vile Parle (Parla) station. Finally it crashes into the CST Station, which is actually in the opposite direction to the direction of travel shown earlier.