You don't get out of your tomb much.
We're not saying you're a grave robber, but if you are: seriously, stop doing that! So before you start robbing graves, consider who you're affecting with your actions. Explain this costume then. Take advantage! You're hanging out, just chilling, neatly swirled in your mummy wrappings, and suddenly some guy starts creeping in your tomb, looking at your golden urns or your Xbox or whatever else a mummy keeps in his tomb. Obviously, mummies are real and they're pissed.