Boobies are no doubt a weird fly. I don't know what they necessarily imitate, if anything, or why they work. I just know that I've experienced many days when they seem to catch fish to the exclusion of just about anything else. Between the buoyant foam eyes and the typically densely wrapped body, they tend to move very erratically when fished on a sinking line and they push a lot of water, which produces a sonic footprint that fish can sense. There is something about these qualities that make trout want to absolutely destroy boobies at times and I've found it pretty rewarding to carry a small selection in my box for those days when other flies can't seem to seal the deal.
The Pumpkinhead Booby in my mind actually looks somewhat like a dragonfly nymph and seems to work really well throughout the summer and early fall in a lot of lakes, but I'll tie this same profile fly in all sorts of gaudy colors like fluorescent orange and pink or chartreuse and black and enjoy surprising success. An all white version seems to be especially effective in the fall. Cast as far as you comfortably can on a full sinking line with a stout leader 3-4' long, count it down to the appropriate depth and retrieve it in short quick strips. Hang on tight to your cork because there is seldom much subtlety to the way trout hit these things.