Herndon (1983)

A high-school nerd, Herndon (Richards), grows up to be a clumsy but genius computer scientist though he's still a nerd and goes to his 10-year reunion where he learns that his arch nemesis, the school jock, Shack (McGinley), is in need of a job. Herdon reluctantly hires the jock on as an assistant and it doesn't take long before everyone thinks Shack is in charge and Herndon's life grows miserable.