Don't Worry, We'll Think of a Title (1966)

Charlie Yuckapuck is mistaken by Klavashian intelligence agents for a defecting cosmonaut named Yascha Nudnik. Charlie works in a diner with his friends Annie and Magda. When Magda inherits a bookstore, Charlie and Annie go to work for her, unaware that the bookstore is crawling with spies seeking to recover secrets stolen by the missing Nudnik.