Kakkakuyil movie is about Sivaraman(Mohanlal) who has come to Mumbai for a visa. But Sivaraman finds his friend Govindan Kutty (Mukesh) amidst a sea of problems. Sivaraman is forced to participate in a bank robbery planned by Thomas and his gang, which puts them in more trouble.
And they find a place as Kunjunni with the body of Govindan kutty and sound of Sivaraman in the house of a blind old couple (Nedumudi Venu and Kaviyoor Ponnamma), whose grandson Kunjunni who had left them a long time ago (when he was 7) and is now coming home.
But a turn of events finds Sivaraman and Govindan kutty (combined) as Kunjunni with the body of Govindan kutty and sound of Sivaraman.