Knight's Code of Honor, Rule #1: Never leave the castle without proper garb and your family crest.
To make each tunic, cut a long rectangle from a silver or gray plastic tablecloth (we started with a 108- by 54-inch cloth from a party store, which made seven 15- by 54-inch tunics).
Fold the rectangle in half lengthwise and cut a hole for the head.
From self-adhesive stiff felt sheets, cut a crest for each child (we made some of our 8- by 9-inch crests from one piece of felt; for the two-toned crest at left, simply cut half a crest from each color).
From the scraps, cut decorative shapes, such as lions and crowns. Click here for a printable crest pattern and five shape patterns.

Stick the crests to the tunics, then let the kids personalize them with their knight name, foil tape (as shown above), felt shapes, stickers, and markers.
See A Medieval Birthday Party