The film stars Kamal Haasan, Jayaram, Devayani and Jyothika, with Delhi Ganesh, Charle, Ramesh Khanna and Madhan Bob in supporting roles.

Thenali, thinking it is a fake bomb used only to relieve him from his fears, removes it and puts it in Kailash's house for future use where it explodes.

[5][6] Due to Haasan's commitments to Hey Ram lasting almost a year, Ravikumar spent the time by "writ[ing] a few stories" for him.

Hameed played a major role in penning dialogues for scenes involving issues related to Sri Lankan civil conflicts.

Hameed spent over a month in dubbing and production of the film project with the intention of assisting Haasan to train him speak in Jaffna Tamil.

[15][16] Simran has stated that, though she liked the script, to her dismay the role required body exposure; she therefore demanded an exorbitant fee so that she would be rejected, and succeeded.

[18] Devayani, who portrayed Kailash's wife Jalaja, accepted to act in the film at Ravikumar's request, without asking about details such as the story or the lead actor; she later realised that she would not be paired opposite Haasan, but did not mind being side-lined by Jyothika.

[21] Meena, who had been approached by Ravikumar to star in some of his earlier films but declined due to unavailability of dates, was asked to do at least a cameo in Thenali, and agreed.

[22][23] Yugi Sethu has stated that he was offered to act in the film by Haasan, but was unable to accept due to his commitment to the TV series Nayyandi Durbar.

[24] The film was launched at the Kalaivanar Arangam in Chennai on 22 March 2000 with Y. G. Mahendran as compere and with Rajinikanth as chief guest.

[27] While filming the scene where Pancha Bhootam and his assistant jump into a lake, Ganesh and Ramesh Khanna did so despite the "freezing temperature".

While filming other scenes, Haasan was the only one wearing a coat; the other cast members including Devayani and Jyothika had to "brave the temperature and get wet in the rain for a sequence".

Ravikumar recalled how the card was created: "We shot in high speed, and at the count of five, asked him to wink and smile.

[37] Rahman initially refused Ravikumar's offer to work on the film due to numerous Bollywood and international commitments.

[41] The song "Swasame" is set in Hamir Kalyani raga,[42] and was re-used in the final scene of the 2009 American film The Accidental Husband.

[51] Malathi Rangarajan of The Hindu gave a verdict that the film was a "wholesome mix of rip-roaring action, witty dialogues and exotic locales".

She was particularly appreciative of Jayaram's performance, Haasan's Sri Lankan diction and his comedic prowess, "both the physical and dialogue-oriented kind", adding, "Logic has no place in the story, which is only meant to make you laugh".

[8] Visual Dasan of Kalki lauded Haasan's delivery of Sri Lankan accented Tamil, but said the real show stealer with regards to acting was Jayaram.

[53] Tamil Star wrote that Ravikumar, Mohan and Haasan "have offered an enjoyable comic fare", but criticised the music, though the reviewer said "it is to be commended that each lyricists has put in his best in his lyrics".

[54] Writing for Chennai Online, Malini Mannath said, "Kamal's perfect timing for comedy, matched equally by Jairam, the antics of Delhi Ganesh and Ramesh Khanna, the humour, some situational, some slapstick, and Crazy Mohan's lines sustain the film for sometime.

[55] Indiainfo lauded Haasan's "flawless" Sri Lankan accent, but felt the film had "nothing new to offer", criticised the music, dance choreography and cinematography.