A positive vibe permeates the movie set of “The Weekend on Cape Cod When Everything Changed,” which is being filmed in Mattapoisett this month. Working long hours, the do-it-all staff improvises daily to provide support and supply nourishment for actors and crew. The story follows an Iranian immigrant who marries her billionaire boss's son to maintain her American visa, but the green-card arrangement encounters unexpected challenge when the bride’s besties bring boyfriends with their cross-cultural baggage.