Every so often, life takes you completely by surprise. There is no better in-over-your-head costume than Brad from The Rocky Horror Picture Show
To pull off Brad you essentially have to look as normal and boring as possible; the way to that of course lies in the dark blue V-neck sweater vest. Practice saying "Hi, my name is Brad Majors, and this is my fiancee, Janet Weiss."
Then you'll need slate gray pants, a black belt and brown loafers. Feel the boring, be the boring.
To top it all up you'll need a light blue button-up, black thick rimmed glasses and a tan zip-up jacket with an optional "Denton High School" patch. The patch lets everyone know you conform.
Whether you're served the remains of a partial brain donor for dinner, or being seduced by a transvestite you think is your wife, this outfit will serve you well!