Raja(Karthik) feels stifled under his strict father Col.Chandrasekhar(Jaiganesh) and when his father picks a girl he doesn't like for him to marry, it is the last straw and he runs away to Ooty. There he teams up with Vasu(Koundamani) and they come up with an ill-advised plan to kidnap Indu(Rambha), the daughter of Vishwanathan(Manivannan). Vishwanathan is infact Col.Chandrasekhar's friend and it is Indu that Raja was supposed to marry. But Vishwanathan now mistakes Vasu to be his friend's son and takes him under his wing while Raja is hired to be his driver.

While the movie is not a continuous comic ride, it succeeds in raising laughs at regular intervals. While the handling may be lightweight, there is nothing light about the story. There are several twists and turns that perk it up at key moments and make sure that the comic momentum never flags. While the story of mistaken identities is itself quite common, Sundar periodically introduces subplots like the plans of the two managers to murder their boss and new characters like the second Manivannan. These are twists that help in propelling the story forward without any slowdown.

The movie has a rich stock of one-liners to throw at us and quite a few of them find their mark. But unlike movies that rely purely on one-liners and lose steam after a while, Ullathai Alli Thaa also boasts of many sequences that are quite hilarious. The scene where almost the whole cast ends up in Jyothimeena's house(but with vastly different motives) is one such sequence. The scene, which has them scrambling around to find hiding places, is expertly choreographed and presented. The scene where Karthik and Koundamani negotiate with the fake kidnappers over the phone is another successful scene. Koundamani's reactions as the ransom inexplicably goes lower are hilarious.

There are some smaller sequences too that manage to tickle our funny bone and Sundar makes sure that none of these extend out too long to exhaust the laughs. The parts where Karthik and Koundamani have to dupe both Jaiganesh and Manivannan at the same time are clever and funny. Senthil and his partner do their part with their hare-brained schemes to dispose off Manivannan. The comic vein extends till the climax with Karthik and Koundamani spouting several funny lines in the villain's den.

Ullathai Alli Thaa gave us two stars who were familiar to moviegoers from before but had now changed their images and went on to hit it big after the movie. Rambha had been seen before as a rather unglamorised village girl in Prabhu's Uzhavan. But with this movie, she walked directly into the dreams of moviegoers right from the first scene, where her sizzling red dress blows up Marilyn Monroe-style. Manivannan too had appeared onscreen in movies like Kodi Parakkudhu and Amaidhi Padai but as a villain. Here he took on a comedy role and a double role no less and became the new comedy czar of Kodambakkam, relegating to the background, the popular team of Koundamani and Senthil.

Karthik puts his unique dialog delivery to good effect and gains nice comic mileage out of his lines, especially during his initial conversations with his strict father. Koundamani too delivers several laughs with his typical style though it is loud at a few places. Senthil is subdued with not much to do while Jyothimeena has a role with no dances - something new for the actress who is accustomed to appearing in single song sequences. Jaiganesh, who passed away recently, strikes the right note in his performance as the ex-army man with a secret. Almost all songs were hits and rightly so with Sirpi concentrating on catchy tunes. Azhagiya Lailaa..., which has Mano singing in a different voice, I Love You... and Adi Anaarkali... are all catchy. Chittu Chittu..., copied from a Punjabi tune, is picturised well with the whole cast participating in the proceedings.