As the title indicates, Appa dwells on the role of fathers — how they bring up their kids becomes a deciding factor in their children's lives. Like some of his previous films, in this one, too, Samuthirakani touches upon a few socially relevant issues. To start with, there are three fathers — Dayalan (Samuthirakani), a humanitarian who has high hopes on society, Singaperumal (Thambi Ramaiah), a self-centered person who is concerned only about his ambitions, and Nadunilaiyan (Namo Narayana), a well-calculated man who always prefer to be on 'safe side' in life.
The story kicks off when each of them is blessed with a child, and they try to instil their philosophy of life into their respective kids. Dayalan's wife can't digest the fact that the former wants their son, too, to adopt his progressive ideologies. All hell breaks loose when she realises that her husband is planning to make their child Vettreeswaran (Vignesh) a 'good person' than a 'well-educated' man with a white-collar job. On the other hand, Singaperumal is keen on making his son Chakravarthy (Raghav) a doctor, despite a not-so-effective protest from his wife. His principles and insistence on an over-disciplined lifestyle become a nightmare for Chakravarthy. Nadunilaiyan, too, brings up his child Mayilvaganam (Nasath) in a way that he wants him to be — asking him to stay away from all sort of issues which would lead to an uneasy life. His wife, however, has little say at home. The story focusses more on the relationship between Dayalan and Vettreeswaran, and the father-son episodes are a delight to watch.
As all the children grow older and reach their mid-teens, each of them chooses a career — quite obviously, Vettreeswaran succeeds in pursuing what he likes, thanks to the guidance of his father. Chakravarthy struggles to meet his father's endless expectations. Interestingly, Mayilvaganam manages to put up an impressive show in his area of interest, despite a not-so-common physical problem and discouragements from his father.
Meanwhile, Vettreeswaran and Chakravarthy fall for (read infatuation) girls (played by Gabriella and Yuvalakshmi respectively), whom they happen to meet at different situations. Dayalan, who has been successfully maintaining a friendly rapport with all the children, including the girls, becomes a reliable father figure for them. Even as the plot moves at a slow pace, an unexpected tragedy hits them putting one of these lives in danger. Nadunilaiyan feels bad when he realises the mistake he has been doing to his son all these years, while Singaperumal has to pay for his unjust deeds.
Despite the sluggish narration at a few places and the clumsy making, Appa, for sure, throws light upon a few issues which need to be addressed promptly. Prominent among them is the little-known horrible life students lead in the educational institutions and the manipulation which influential people resort to, for justifying the wrong doings. Samuthirakani excels as an actor again, though this is not one of his best roles. However, as a director, he gets too preachy. Thambi Ramaiah puts up an impressive performance. It is the little boy Nasath who is the attraction of the film, while Vignesh, Raghav and the girls are apt. The music by Ilaiyaraaja hardly contributes to the film, as does Sasikumar's brief appearance.
