If angels appear on Earth, they're wearing overcoats. Usually winter-weight, wool, 3/4 length overcoats. Sometimes trenchcoats. The trope frequently appears in movies where angels walk among humans, serving as a kind of Uniform Trope to communicate the wearer's angelic nature. As far as this troper can tell, it originated with Wings of Desire (1987). Due to overcoat-wearing badass angels in such sources as The Prophecy and Dogma, there is often some overlap with Badass Longcoat. Subtrope of Our Angels are Different.
- Wings of Desire, likely Trope Maker. All angel characters, in particular Damiel and Cassiel, but also the secondaries, are all wearing smart wool overcoats during their Earthly tenure. Damiel gets to keep his overcoat even after becoming human.
- Faraway So Close, sequel to Wings of Desire, focuses on Cassiel and Raphaela, once again in their woolen coats.
- City of Angels, a remake of Wings of Desire, sees angel Nicolas Cage in a wool overcoat.
- The Prophecy. Eric Stoltz's Simon, in particular, wears the standard issue heavy-wool version. Evil angel Gabriel (Christopher, ehm... Walken) wears a lighter coat, though it still fits the trope.
- Dogma has its nogoodnik angels Bartleby and and Loki (Ben Affleck and Matt Damon) in wool overcoats, worn over hooded sweatshirts. Alan Rickman's creation-weary but non-evil Metatron also wears a hoodie, but under a shorter jacket. (Creator Kevin Smith identifies Wings of Desire's use of overcoat-as-angel-uniform as the inspiration for having his angels wear a unifying article — in this case, the hoodie. The overcoat look for Bartleby and Loki undoubtedly originates from the same source.)
- Guardian angel Clarence from It's a Wonderful Life wears an overcoat, but it's winter in Bedford Falls, and everyone's wearing an overcoat, so it's not clear that this counts as an example.
- Although it's autumn in Iowa and everyone's wearing overcoats, the titular angel in Michael wears a trenchcoat most of the time, indoors and out, specifically to hide his wings.
- Angels in the film Gabriel are depicted wearing various longcoats. Gabriel spends most of the movie in a brown trenchcoat. Fallen angel Sammael highlights his evilness by wearing a black leather trenchcoat.
- Supernatural's angel-in-residence Castiel sports a trenchcoat. Wings of Desire and John Constantine from the Hellblazer comic are acknowledged as inspirations for his look.
Hello, Unknown Troper. You'll need to get known to lend a hand here.