The Great Grand Superhero follows Dipu (Mihir Godbole), a young boy struggling to find his place in a new school. In an attempt to impress his classmates and make friends, he spins an extraordinary tale—that his grandfather, Jagdish Chandra (Jackie Shroff) is a real-life superhero. What begins as an innocent boast quickly spirals out of control as his curious classmates demand proof. Adding to the chaos, Grandpa confidently backs up the story, claiming it is absolutely true—with one unusual condition: his superpowers only emerge when Earth is threatened by an alien invasion. As skepticism grows and expectations mount, a series of surprising and entertaining events unfolds, leading Dipu and his grandfather on an unforgettable adventure.