All you really need for this one is a white lab coat that you can get at any uniform warehouse. Take the coat into the garage or outside, and splash it with fake blood. Let it dry overnight. Stick some test tubes, a rubber rat, and anything else you can thin of into the coat's breast pocket. You can get a wig to match this outfit or just use lots of gel and mousse to make your hair stick straight out from your head. Wear a pair of wire glasses (thrift shops usually sell used glasses) and you are officially a crazed lab looney let loose.