Design the silhouette first—something sleek that shrouds the wearer in shadow, then add a bright, unexpected detail that pops when the lights dim. Keep the costume simple at the start, but hide a second layer of color or a hidden weapon that reveals itself at the twist point. Use contrast: dark fabrics with a single metallic or neon accent, make the audience stare, then pull the accent out in the climax. Timing is everything; move fast, stay ruthless, and let the audience taste the darkness before you let it spill into laughter.