In a tiny concrete-and-tin Chennai home in the slums live two young brothers with their mother and grandmother. With the boys' father in prison for unknown reasons and with an ageing mother-in-law, the mother does her best to keep the kitchen fires burning. The brothers spend their time playing games and stealing and devouring eggs from crows' nests. Their love for these eggs leads them to start calling themselves "Periya Kaaka Muttai" ( Big Crow Egg) and "Chinna Kaaka Muttai" (Small Crow Egg).
The young boys constantly beg their mother and grandmother for toys they cannot afford, and later for a television. They don't yet understand that the two women can't give them everything they want. When their mother and grandmother finally do bring home a television – a gift from the government to ration card holders who live below the poverty line – it's like the opening of a portal. The boys see a pizza commercial on TV whose steaming, slow-motion images make the unfamiliar food look like manna from heaven. Meanwhile, a brand new pizzeria comes up in the neighbourhood, and actor Silambarasan alias Simbu comes to its opening. Remembering the looks of enjoyment on Simbu's face when he tasted a pizza at the pizzeria, the boys thereafter think of nothing else but getting their first taste of a pizza.
The brothers go to the railway tracks each morning to collect the charcoal that falls off goods trains. They sell the charcoal at a scrap metal shop and are paid for their trouble. They usually hand the money over to their mother who is saving up to pay their lawyer to get her husband out of jail. But once the boys become aware of the cost of a pizza, they begin saving the money for themselves instead, lying to their mother that they have not collected any charcoal since they were out playing.
The boys succeed in saving the ₹ 300 required to buy a pizza, but are shooed away by the watchman of the pizza shop since they are badly dressed, which reflects the fact that they are local slum-dwellers. The boys narrate this story to their friend Pazharasam who works as a lineman with the Railways. He tells them that people place a lot of importance on clothes and advises them to save up and purchase new dresses before approaching the pizza outlet again.
The boys go on to work again to save money for buying new clothes at Chennai Citi Centre. In the meantime, they show their grandmother the pamphlet from the pizza shop. She tries to make them a home-cooked pizza using dosa batter as base, but the boys deride her attempts and insult her.
After finally saving up enough money for new dresses when the boys see Citi Centre, they realise that it is another big mall which would definitely not allow them inside. But they somehow manage to acquire a newly bought pair of clothes from a couple of rich children by buying them panipuri from a street vendor, much against the wishes of the rich boys' father, who had denied them the treat as he considered it unhygienic.
The happy brothers return to the pizza shop in their new dresses. Another group of slum boys who are envious and sceptical about the brothers' story about going to eat pizza follows them to take a video of what transpires with the brothers at the pizza shop. The brothers are once again confronted by the watchman and he now forces them to go home right away but the boys protest by saying that they have money and are wearing new clothes. This argument attracts the attention of the pizzeria supervisor who comes out and slaps the older brother. This is caught on video by the other slum kids who laugh at the brothers' humiliation.
The sad and disappointed brothers return to their slum only to be further overwhelmed by the miserable sight of their dead grandmother. The brothers feel guilty when they remember insulting their grandmother some time before.
When two men in the slum happen to watch the video of the boy being slapped, they try to make money by threatening the owner of the pizza shop to release the video to the media. The owner realises he could be imprisoned and his pizzeria sealed by the government due to his supervisor's act of discrimination and violence against slum children. He offers one of the men a hundred thousand rupees for not making the video public. The man agrees, but his associate releases it to the media hoping to make some money (unaware of the huge sum being offered). This stirs up tension amongst the pizzeria's owners who finally decide to publicly apologise to the slum kids.
The boys are welcomed to the pizza spot in a red carpet reminiscent of Simbu being welcomed in the opening ceremony of the pizzeria. The owner also promises them free pizzas for life. Even as the brothers begin to finally enjoy their first pizza, they tell each other that the dosa-pizza which their grandmother had earlier made for them had tasted much better.
The first look of the project was announced to the media by Padma on 26 January 2014, coinciding with Republic Day, with Dhanush and Vetrimaaran announcing that they would be making a children's film to be directed by M. Manikandan, a former wedding photographer, who had earlier directed the short film, Wind (2010), with music by G V Prakash Kumar. Filming for the project began at the end of May 2013, with the maker suggesting that the film would be complete in one schedule. Silambarasan accepted to make a cameo appearance in the film. He joined the team in September 2013 to film scenes alongside Babu Antony who plays a landlord. Two newcomers, Ramesh and Vignesh, had been selected to play the lead roles along with Iyshwarya Rajesh and Ramesh Thilak. In August 2014, it was reported that the film had been completed four months before.
A The Hollywood Reporter reviewer called Kaaka Muttai an allegory for the vast class differences in India, where some people profit off a system leaving little room for advancement for those below.
The music of Kaaka Muttai was composed by G. V. Prakash Kumar.
The film was selected to be screened at the 39th Toronto International Film Festival (TIFF) and had its world premiere on 5 September 2014, where it received a standing ovation. It became the first film by a debut Tamil director to have its world premiere at Toronto since the festival's inception in 1976.
The film was furthermore screened at the Rome Film Festival, 2014, the Dubai International Film Festival, 2014, the Brisbane Asia Pacific Film Festival, the Indian Film Festival of Los Angeles (IFFLA), 2015, and at the Gold Coast Film Festival, 2015. The satellite rights of the film were sold to STAR Vijay.
Kaaka Muttai received universal critical acclaim upon its theatrical release on 5 June 2015. Baradwaj Rangan called Kaakka Muttai an "outstanding debut" by Manikandan, going on to add, "This is one of the most assured debuts I've seen — one deserving of more than just that consolation-prize-of-a-National-Award...Kaaka Muttai is so entertaining that it’s easy to forget how sad the undercurrents are". Indo-Asian News Service gave it 5 stars out of 5 and wrote, "Kaaka Muttai is a little gem that's highly recommended and deserves to be celebrated". The Times of India gave the film 4 stars out of 5 and wrote, "Manikandan's Kaaka Muttai is multi-layered; on the surface, it is all warm and inviting — a feel-good film about two kids and their simple desire and the earnestness in the filmmaking invites comparison with Iranian films like Children of Heaven...there is a hard base to it as well and from time to time, the film turns into a commentary on the class divide in our society and how it is exploited by wily politicians, an allegory of the effects of globalisation, and even a satire on media's obsession with sensationalism". Rediff gave it 4 out of 5, too, calling it a "a delightful entertainer with a subtle message", "brilliant" and "definitely a must watch". Firstpost wrote, "Kaakka Muttai (is) one of the most charming films you'll see this year. It's beautifully shot, without making either slums or poverty look photogenic and exotic".
Udhav Naig from The Hindu wrote, "Award-winning films have a troubled reputation amongst the general film audience. These films are brushed aside as ‘high-brow’ and ‘slow’. Debutant filmmaker M Manikandan’s Kaaka Muttai...breaks from these imagined prejudices: Kaaka Muttai is a highly entertaining film, with a spotlight on poverty". Sify wrote, "(It's) A charming little treat of a film...Held together by a sharp screenplay that throws up some pleasant surprises, this film is light, easy and enjoyable. The film works because it is intelligent and uncompromising". Deccan Chronicle gave it 3.5 stars and wrote, "with unenhanced visuals that gives a sense of verisimilitude, acting that isn’t staged and dramatised in any obvious sense, and more importantly, characters that bring alive a subsection of the populace, Kaakka Muttai is sure to make you at least a slightly better person than you were before, owing to the reflective power of the film". Livemint wrote, "the film invites us to admire the resourcefulness of the two siblings without turning them into objects of pity or sentiment. It’s the strangest feel-good film you’ll see this year: two kids in rags, happily walking past piles of garbage, their heads full of pizza". Bangalore Mirror wrote, "film goers as well as critics hold an opinion that films that bag awards and travel wide across the globe are slow while the screenplay unfolds and dull as well as dreary in treatment. Young filmmaker M Manikandan breaks that myth. The film is lively and interesting right from the first frame where the two little boys are introduced".
In the first two days, Kaaka Muttai collected ₹ 2.4 crore, which, according to trade analyst Trinath, was a "phenomenal" figure, considering the film had no star cast. The film's opening weekend gross was estimated at ₹ 3.37 crore, and its first week gross at the domestic box office was estimated at ₹ 7.1 crore. After one day, the film had earned ₹ 8.6 crore, according to Taran Adarsh. In the fourth week, the film grossed ₹16 crore (US$2.5 million).