at SFlix. H.M.S. Pinafore; or, The Lass That Loved a Sailor is a comic opera in two acts, with music by Arthur Sullivan and a libretto by W. S. Gilbert. Earning rave reviews during its run at the Stratford Festival in Stratford, Ontario, this production takes a tongue in cheek approach to British class structure, the admiralty and the ruling classes. It's also a love story with a multitude of permutations.