If you could trust anyone to put a different spin on Medieval England, it would be “Tiny Furniture” and “Girls” creator Lena Dunham. She certainly has the right source materials for it — “Catherine Called Birdy” is an adaptation of Karen Cushman’s 1994 novel, lauded for its comedic, but sympathetic, take on the role of young women in the Middle Ages. In England in the year 1290 CE, Catherine (called Birdy by her family and friends) is the youngest daughter of Lord Rollo and Lady Aislinn. With his debts mounting, the perpetually frivolous Rollo views his teenage daughter as a potential financial windfall awaiting only the right suitor. Birdy, however, has other ideas, with no intention of fulfilling her expected societal role and playing dutiful wife to any lord with the money to salve her father’s overspending. Bella Ramsey (“Game of Thrones” and the upcoming adaptation of “The Last of Us”) has a ball — with exactly the kind of creative abandon you would expect from a Dunham-directed project — as the rebellious teenager who resorts to increasingly complex and inspired schemes to put off potential suitors and outwit her father. “Fleabag” and “Sherlock” star Andrew Scott is excellent as Rollo, and the relationship between the two gives this movie a surprisingly emotional heart. Others in the ensemble cast (including Lesley Sharp as Catherine’s nursemaid, Billie Piper as Lady Aislinn and Joe Alwyn as Catherine’s dashing Uncle George) appear to be having an equally exhilarating time. For while there’s little of substance going on here, it’s all done with such relish and gusto that it’s hard not to get swept up in this riotous showcase of an excellent cast poking fun at ‘Ye Olde England’ tropes. While the movie feels a little long, the story stretched a little thin, and the ending (a slight change from the novel’s conclusion) is conveniently neat, this is still a whole heap of fun. A silly film, poking fun at a silly period of history — but with a director and cast capable of pairing smarts with entertainment.