Kareena Kapoor was writer/director Imtiaz Ali's first choice for the role of Geet. Even though he wasn't particularly a fan of hers and hadn't seen her in many movies, he knew she would be able to look natural without makeup, be hyper, talkative and interesting but not irritating.
Kareena Kapoor and Shahid Kapoor who play lovers in the film were also dating in real life - until they broke up whilst making the movie.
Writer/director Imtiaz Ali only settled on Shahid Kapoor for the role of Aditya after meeting him, as he previously viewed him as a "forgettable actor" before realizing that he had "gone through a lot in life and that maturity had never been brought out" and that as such he was perfect for the part of a "young, mature, quiet guy."
The producers had first signed Bobby Deol in 2005. The film had many working titles at the point. "Geet" was one of them. Bobby told the producers to sign Imtiaz Ali because he was very talented .The producers wanted Kareena Kapoor for the film , but Kareena refused to even meet Imtiaz Ali. That is when Bobby suggested they approach Preity Zinta. She agreed but needed six months before she could shoot. This is when Kareena told the producers she would sign the film only if they replaced Bobby Deol with her then boyfriend Shahid Kapoor . The producers agreed and replaced Bobby Deol without even informing him.
Dehli's PVR Cinemas held special screenings of the film on Valentine's Day 2008 to celebrate its 100 days run at the box office.
As part of the film's promotion, the producers painted two full local trains in Mumbai from the Western and Central lines with imagery from the film, with Shahid Kapoor present to chat with fellow passengers and inform them about the movie.
The number of prints for the film across India was increased in its fourth week of release due to popular demand and the lower-than-expected performance of Saawariya (2007).
The title of the film was decided by a popular vote. The other choices were 'Punjab Mail' and 'Ishq Via Bhatinda'.
A private screening of the film was organized at Yash Raj Studios in Mumbai for those associated with the film and their families on October 23rd, 2007.
At one point Bhumika Chawla and Bobby Deol were to head the cast, with the film titled "Train."
Yeh ishq haaye choreographed by Saroj Khan recieved national award , as background dancers ,were almost non dancers ,locals of the area and managed to pull out the steps
The 2010 Hollywood movie "Leap Year" starring Amy Adams is heavily inspired by this film.
Kareena Kapoor was seen waltzing to the song "Walking on sunshine" by the 1980s American rock group Katrina & The Waves in the first promotional clipping of her just released "Jab We Met". But suddenly the song vanished from all promos! Director Imtiaz Ali reluctantly admits the song was pulled off due to copyright issues."It went perfectly with Kareena's character and the film's mood. In fact, I didn't want to use it in just the first promo but all the promotional campaigns and also as part of the background music in my film," Imtiaz told IANS. Alas, Imtiaz just couldn't track down the producers of the song "Walking on sunshine". "The song was recorded in 1985. The band is now defunct. We couldn't source the song to its origin."Rather than risk a copyright-infringement situation, Imtiaz decided to pull the plug on the track.This latest incident of copyright consciousness in Bollywood is part of a larger campaign to acknowledge and legitimise all derived works in Hindi cinema, especially after the makers of "Partner" were accused of snitching "Hitch" without permission.