Crew or equipment visible: At the start of the song "Dewana Hai Dekho" when Hrithik Roshan opens the door of the red car, the cameraman is reflected in the door.
Continuity: Before the song "You Are My Soniya", when Poo is hitting on Rohan, she is wearing two different shoes. Then in the song she is wearing two of the same shoes.
Errors made by characters (possibly deliberate errors by the filmmakers): Years later when Rohan meets Pooja again, after he recites the tongue twister "Chandu ka Chacha," he says he finally got it. But he forgets to say the line "chandni raat mein," so he doesn't get it right.
Anachronisms: After Hrithik comes to stay at SRK's home in England, one morning Hrithik gives a lift to SRK to his office as his car tire is punctured. On the way, they put on a match commentary. The match is taking place in England (Oval) and it is morning. They say that only last over is remaining and after some time they declare that India has won. The match is ending around 9 - 10 AM so would have to have started around 2AM.
Anachronisms: Amitabh Bachchan and Jaya Bachchan dance to the song "Aati Kya Khandala" in 1991. However, the song came out in 1998.
Factual errors: When Anjali's son performs the Indian National Anthemn impromptu at an English school function, the crowd automatically stands to attention as a sign of respect. However English people are largely unfamiliar with the Indian National Anthemn so would not have understood it's significance.
Errors made by characters (possibly deliberate errors by the filmmakers): The trend-setting Pooja's nickname at her English school is 'Poo', a name that would've bought her much ridicule rather than idolization, as the word 'Poo' is everyday English slang for excrement.
Errors in geography: In the storyline, the Raichand offices and main home are supposedly located in India, but the offices shown are clearly Canary Wharf in London and the main home shown is actually Waddesdon Manor in Buckinghamshire. The helicopters used to transport people supposedly in India, clearly have British registrations shown.