I think most people look through their slices first, to see if they got anything, before risking their dental work.
King cake usually is very rich, especially if it has an almond paste or cream cheese filling, and one slice is definitely enough for most people.
In the Southern U.S. where it is most often eaten (in that country), it's usually decorated with purple, green and gold sugar for the Mardi Gras colors, and has white icing piped on it. This can vary, but this is a common theme. Some people also decorate the plates with Mardi Gras beads or "doubloons" (coins thrown from floats or used as decoration).