the lazy costume

I like the idea of casual costumes. does such a thing exist? Kind of the same idea as a tuxedo tshirt. you're expressing a complicated, rather fancy sentiment in a laid back, casual way. most people probably wont even know its a costume, but I can still feel nifty while wearing it.
This is a t shirt I modified recently to be a star trek next generation starfleet uniform inspired tee shirt! I can wear it in an everyday setting or to something cooler, like a marathon watching night with friends or something. (the com badge is a pin from the new reboot, but I don't have a next gen version and I haven't got around to making one.)
What I like about this shirt is that without the pin or with a cardigan over top, it looks like a plain ol' regular t-shirt, meaning I can basically wear a star fleet uniform anywhere.