The film begins with a trio of friends in college (Malar, Mona, Gayathri). Mona falls in love with Karthik (Shiv Pandit) despite the advice of Malar (Manasi Parekh Gohil) who suspects Karthik to be a complete flirt. One day, while on a date, Mona mentions to Karthik, Malar's views about him and this gets Karthik to start disliking Malar for interfering in his love life. When Karthik calls Mona, Malar picks the call up accidentally and they get into an argument with Karthik venting out his anger towards her interfering in his love life. Shortly later, he breaks up with Mona. Gayathri believing Mona was a wrong choice in Karthik's life begins to date Karthik, while Malar is firmly against it. The relationship ends the same way as his relationship with Mona. A year or two later both Karthik and Malar work at the same software company on different floors in the same building. One day, while trying to call his friend on Malar's floor, he accidentally calls Malar and the two realize their identities and presence in the building and the age-old feud resumes. Over lunch, both Malar's friend (Vicky) and his own friend (Suja) advise him to sort it with Malar. Vicky questions why Karthik would fight with such a beautiful woman as Malar. Karthik not knowing what Malar looks like decides to take a look at her. When he sees Malar he falls in love at first sight, he then tries to reconcile with Malar, but Malar is not willing to forgive a flirt like Karthik. Karthik becomes desperate and begins to follow Malar and in a chance meeting orchestrated by Karthik he introduces himself as a sweet and kind person by the name of 'Sundar'. Malar who has never met Karthik face to face, believes his false identity and begins to open up to Sundar. They start to get to know each other and meet often, when one day Suja who works with Malar finds out about his game. Suja gives Karthik the ultimatum to reveal his true identity, once Malar declares her love for Sundar. Karthik tries to salvage his relationship with hilarious consequences. But, all said and done, how Karthik reveals to Malar about his true identity and her acceptance or rejection forms the crux of the story. Vicky (Santhanam) provides comic relief to the story.Shiv Pandit as Karthik/Sundar
Manasi Parekh as Karunai Malar
Santhanam as Vicky
Suhasini Raju as Suja
Maya as Mona
Vibha Natarajan as Gayathri
Lakshmi Ramakrishnan as Karthik's mother
Andrew Louis met Ravichandran and narrated the script of Leelai and two months later he agreed to produce the film. The producer subsequently moved the film on to the hands of his brother, Ramesh Babu, under the subsidiary company 'R Films', which was also making Ravi Varman's Moscowin Kavery at the time. The director selected North Indian actor Shiv Pandit in the lead role after seeing him an advertisement for a mobile phone company, Airtel. After Pandit was signed on, he practised his Tamil dialogues by reading them repeatedly and understanding the emotions and punches. He also watched a lot of Tamil films to get attuned to the culture. The female lead in the film is played by Manasi Parekh who has been part of popular shows on Television such as Star One’s India Calling and Star Plus's Gulaal. A major portion of the film was shot in the popular software company 'HCL' (Chennai Office). The song "Oru Killi" was shot at the Maheshwar Fort in Madhya Pradesh, while the other songs were shot in Goa and Puducherry respectively.
The film ran into a legal battle over its title Leelai with another film claiming it as their own. Ravichandran eventually won the case, forcing the other film to change its title from Leelai to Naan Aval Adhu. The film had been ready for release since 2010, with Shiv Pandit in between making his début in Hindi films with Shaitan. The failure of Ramesh Babu's other production Moscowin Kavery starring Rahul Ravindran and Samantha, also became a factor behind the delay.
After two years of remaining complete but unreleased, the film was given a fresh lease of life after producer Ravichandran signed a deal to distribute Billa II, dubbed in trade circles as the "hottest film of the year", and thus theatres have shown their support for his brother by giving Leelai a big release. Furthermore, after the success of Oru Kal Oru Kannadi, actor Santhanam's popularity heightened with several of his films being released around the same period such as Kadhal Pisase and Vinayaga to capitalize on his market reach.
Leelai opened on 27 April 2012 alongside another Tamil film Aathi Narayana, and won predominantly positive reviews. Critics from Sify.com gave the film a positive review citing that "Leelai is an enjoyable romantic ride, laced with peppy music and good fun" adding that "the director has worked out the romantic situations and spun it around to make it entertaining". Behindwoods.com mentioned that Leelai is "a light hearted simple romantic tale...a decent family flick for the holiday season". Pavithra Srinivasan of Rediff.com noted that "it's a feel-good, simple, urban romance that has its funny moments and is worth a watch", and added that "Shiv Pandit and Manasi Parekh bring the urban Chennaiite alive - they are expressive, emote well, and nowhere do their lines sound jarring". Vivek Ramz of in.com rated the film 3/5 and noted that "Leelai is a watchable rom-com" and added "If you are game for urban romance, then Leelai is worth a watch for its simple yet realistic treatment with fun". Another critic gave the film three stars out of five, concluding "Leelai may have its drawbacks, yet it is feel-good, fun and engaging. Job well done Andrew Louis". Rohit Ramachandran of Nowrunning.com rated it 2.5/5 stating that "For the most part, Andrew Louis's Leelai is earnest in its narration and interested in its characters".
Despite positive reviews from the critics, the film managed to do average business at the box office mainly due to a complete lack of publicity and predominantly having new faces in the cast. The film also saw a delayed release due to production issues.
The music is composed by debutant Satish Chakravarthy, a classmate of the director, Andrew Vasanth Louis. Satish also wrote the lyrics for two of the songs. The soundtrack released on 24 August 2009, whilst the music composer later stated that he has also worked on a song for the theatrical trailer.