The film initially received extremely negative reviews from both audiences and critics due to the heavy language, sexual content, and drug use along with many other things that were perceived as "inappropriate". However, the film became successful and has become known as a cult film by many young adults and teenagers.
The plot device, where Arup's character (played by Vir Das) shaves his head off after being rejected by the girl he loves, has been apparently borrowed from a real life experience of Aamir Khan, who is also the producer of this film, when he was in his late teens.
Aamir Khan was keen to play the role of Nitin, but opted out as he didn't want to bulk up his weight for the role.
This film was written by Akshat Verma, a Los Angeles based writer, who first wrote the screenplay as a part of his studies at Screenwriting programme at UCLA, under the title Say Cheese. Subsequently, after he lost his job as a copywriter in US, around 2005, he revived the script.Akshat had to compile 15 drafts before the movie went on floors. It took him more than three years to finish writing the story. He visited Mumbai along with Jim Furgele, to unsuccessfully pitch the film to various film producers, eventually after submitting a draft to Aamir Khan Productions, he left. The script was thrown into a pile of scripts in Aamir Khan's office, where Kiran Rao randomly picked it, read it and began to laugh. Soon it was read by Aamir Khan who contacted the writer who was initially hesitant that it might ruin the "clean, family entertainment" tag of Aamir Khan Productions, though Aamir had produced two A-certificate films before, Peepli Live and Dhobi Ghat.
Aamir Khan: There are several mentions and posters for action-star Aamir in an Akshat Varma directed film-within-the-film (Return of Disco Fighter). Aamir Khan is the producer of Delhi Belly, and Akshat is the writer and associate-director. Aamir Khan has a cameo in a song from Disco Fighter at the end.
Kiran Rao: After the jewelry shop robbing scene, the gang escape in a red car. The auto-rickshaw that is behind the car has producer (and wife of co-producer Aamir Khan) Kiran Rao sitting in it.