David Lean's first film in color.
Billy works his work up in the Navy through the film. When he is first seen, he is a Leading Seaman/ Rate having a 3rd Class Quarters Rating in Gunnery. At Reg's wedding, he is now a Petty Officer, with 2 stripes (chevrons) indicating 10 Years Good Conduct, and is still working in Gunnery. When he comes to tell the Gibbons, he has found Queenie, he is now a Sub-Lieutenant, having made the transition from the ranks to the Officer Class.
The comment, early in the film about the cat and buttering its paws, comes from a technique used when a cat moves house. According to this, if the cat has butter on its paws it will stop and lick it of. As cats are very clean creatures, the butter on its paws and the bits of dirt/ dust/ debris that will inevitably stick to it will annoy the cat. The cat will sit down to clean itself and, in doing so, will take in its new surroundings creating a mental map of where its new home is and helping it to make the adjustment to its new surroundings.
The swelling orchestral fanfare which plays over the film's final shots is based around the main theme of the then-popular patriotic song London Pride - a song written and most notably recorded by Noel Coward, the film's producer and author of the play upon which the film is based.
The title 'This Happy Breed' is taken from a monologue of John of Gaunt's in Shakespeare's Richard II, act II, scene i, which is widely renowned for its stirring pro-Anglicism. It reads, in part, 'This happy breed of men, this little world, / This precious stone set in the silver sea, / Which serves it in the office of a wall, / Or as a moat defensive to a house, / Against the envy of less happier lands, / This blessed plot, this earth, this realm, this England.'