A remake of the 1979 Hindi film Gol Maal, it stars Rajinikanth, with Thengai Srinivasan, Nagesh, Poornam Viswanathan, Sowcar Janaki, Madhavi and Viji Chandrasekhar in supporting roles.

Chandran has a moustache; the doctor advises Chandran to take care of the other problems by acting in a manner Sriramachandramurthy appreciates: namely wearing a Nehru jacket for a usual dress given the poverty in the country, always telling his name in full, giving importance to his moustache, behaving decently, showing a lack of interest in sports and drama considering that they do not promote any wellbeing to the home or the country, respecting one's parents, and detesting the concept of having someone else recommend a person for jobs instead of recommending for oneself.

One day, Chandran takes leave by pretending that his mother, who actually died many years ago, has fallen ill and goes to watch a football match.

Remembering the plot of a film his friend, actor Nagesh is shooting, Chandran convinces Sriramachandramurthy that he had seen his moustache-less identical twin Indran at the stadium.

Sriramachandramurthy is, for the most part, scared during the lawyer's monologue, but eventually realises that he is being fooled again — this time by Charuhasan, who is actually an actor hired by Chandran, while Uma was not actually crippled in the chase.

A visibly confused and shaken Sriramachandramurthy locks himself in a room, and comes out with his moustache shaved off, feeling that he does not need something which caused so much trouble.

In June 1980, it was announced that Rajinikanth and Madhavi would star in the Tamil remake of the Hindi film Gol Maal, with K. Balachander directing.

[9] Rajinikanth was initially reluctant to shave his moustache to portray his character, given the success he had with it but ultimately did so, making Thillu Mullu the first film which featured him without one.

Balachander recalled, "Normally I try to get all actors to modulate the dialogue in a particular manner but for this character I wanted Thengai to do it in his style, so instead of teaching him, I asked him how he would like to do the scene and then developed on it.

I wanted him to play it as a character and not as a comedian for I felt that the humour would come out on its own through his unique body language and dialogue delivery".

[14] At Balachander's insistence,[15] Kamal Haasan made a cameo appearance as Charuhasan, an actor posing as a lawyer in the climax of the film.

[19] Film critic Naman Ramachandran identifies one scene where Chandran pulls a prank on the doctor who then remarks that whatever else he accomplishes in life he will always be a good actor, as a "meta" moment.

[1] R. Balu, teacher at Hindu Theological Higher Secondary School claimed the plot of Thillu Mullu and Golmaal was taken from his stage play Casual Leave.

[29] On 1 July 2013, coinciding with International Joke Day, actors and writers of comedy were asked to name their favourite film.