Just Like Dad (1995)

Charlie along with a close friend of his are constantly harassed by school bullies, Charlie has a crush there that he wishes to be able to court, and has a scientist and kind but pacifistic and not particularly attractive appearing father, who is also troubled every now and then by pranksters who also work there. After some failed attempts Charlie does with his father in hopes of qualifying them for the father/son picnic competition, he decides to substitute him by going to a gym and inviting a weightlifter to pose as his father at it. One he comes across agrees to his ploy, and when the competition comes, they succeed. On a count of school pressures following that, the lie about Charlie and his dad spirals out of control and Charlie ends up at the mercy of a kidnapping due to the weightlifter's past involvement with a gang of hoodlums. By that point, not only will the whole truth have to come out to everyone sooner or later whether through Charlie confessing it or by circumstances bringing it about, but it is going to take both the weightlifter and the real father working together to get Charlie out of the mess of being at the mercy of criminals.