Combine bizarre combinations of tops and bottoms. There can be casual tops with formal bottoms or formal tops with casual bottoms.
Fusion themes are great for mismatch day. You can join eastern and western clothing. Or Chinese kimono with a jacket and pants.
Wear loads of accessories that have no relevance to your dress. You can take an umbrella. A Japanese fan, carry a ladies’ purse or wear devil’s ears on your head.
You can combine your sleepwear with normal clothes for a completely mismatched look.
You can also combine guy clothing with girls’ clothing to get a new look.