From Kelli Mahoney's article about:religion - Christian Halloween Costumes
A shepherd costume requires a robe with a rope belt and a shepherd's hook. Robe colors are usually white, brown, or gray, but any color will do. Also, a fun group costume is for one or two people to dress as shepherds while the rest of the group dress as sheep (white clothes with cotton glued on).
DAVID AND GOLIATH:
The key to a good David costume is the slingshot, but you might want to add a short white robe with a sash and a headband. If you have a tall friend the two of you can go as David and Goliath.
THE THREE WISE MEN:
Dressing up as the Three Wise Men for Halloween will probably take some preparation. These are elaborate costumes, but they will definitely be recognizable.
THE HOLY FAMILY:
Going with a robe theme like with David, shepherds and more, dressing up as Mary and Joseph will require a robe for each of you. Jesus is the most simple, because you really just need a doll wrapped in a blanket.
The brilliance of cardboard is that it can be colored and cut into any shape. Cut some cardboard in the shape of the whale and attach it to suspenders or rope to hang over your shoulders. Then you're like Jonah inside the belly of the whale.
THE TEN COMMANDMENTS:
A fun use of cardboard for Halloween is to cut out tablet shaped pieces of cardboard and attach them to rope to hang over your shoulder (like a placard on a person advertising outside a sandwich shop). Dress in black. Color the cardboard grey like stone and write out the 10 Commandments on them.
THE PLAGUES OF EGYPT:
If you have a group of people, each of you can dress as a plague of Egypt. You can decorate a t-shirt with blood, frogs, ping pong balls (hail), lice (and to add effect, mess up your hair like you've been scratching), plastic flies, #1 Son (to represent first born), and locusts. A person can dress all in black to represent the plague of darkness, and another can dress as a sick person as the plague of pestilence. If you're good with makeup, then creating boils on another person won't be a problem.
THE BOOK OF JUDGES:
Dressing up as the book of Judges is more about representation than the book itself. You can dress up in a black robe with a gavel and a Bible.
Angels seem to be a Halloween staple, but they're usually a tried and true Christian Halloween Costume. If you have an all-white outfit, an angel is pretty easy. You can easily make a halo and wings to go right along with it.
There are a multitude of saints to choose from. From Saint Agnes that just requires a white choir robe and a blue shawl to a burlap sack for St. John the Baptist. For St. Francis of Assisi, dress in a brown robe and bring the dog for a walk (he's the patron saint of animals). If you look up a list of Saints, there are probably some creative ways you can represent any of the Saints.
If you have a pair of black pants, then you just need a shirt with a priest collar. You can find these shirts online or at a local costume retailer. Just don't be surprised when people come to tell you their sins and ask for forgiveness.
A nun costume is probably one that will require a little bit of money, as most people don't have a nun's habit handing in their closets. Almost every costume shop carries a nun costume these days.
THE HOLY GHOST:
Ghost costumes have long been a Halloween tradition, it's pretty easy to modify one to be the Holy Ghost. Add the name to the chest, or abbreviate it "HG." You can even just use a sheet and cut holes in it. (But seriously, ask your parents before you start cutting holes in Mom's sheets. There's some pretty cheap white sheets you can buy without freaking your parents out.) You can also try attaching glow sticks so that you glow with the light of the Holy Spirit.
You'll need your friends for this one. You can your friends can pair up as the animals aboard the Noah's Ark. You can purchase animal costumes or even dress in monochrome and just use face paint. Or print animals on t-shirts and go in pairs.
Information and images from about:religion - Christian Halloween Costumes by Kelli Mahoney
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