Annan Thambi movie revolves around Appu and Achu (Mammootty) who are twin siblings who were born with swords drawn at each other and as years pass by, the no-holds-barred bullfight between the two goes on. A highly voluble Appu majestically rules over the Pollachi Market and is wooed by Thenmozhi (Laxmi Rai) who is a niece to his erstwhile-associate-turned-foe Dharmarajan (Rajan P Dev). A dumb Achu meanwhile relives the Puranas in his dad's drama troupe while lamenting a lack of issues even after five years of matrimony with Lekshmi (Gopika).