Regarding "Rear Admiral," I think the answer is probably as disappointing as you feared it might be: it doesn't exist. Here is the actual first draft script excerpt from the Halloween show:
BART: Milhouse. Milhouse, wake up. Quick, look out the window.
MILHOUSE: No way, Bart. If I lean over and put my face against the window, you're gonna smash it, or maybe pinch my butt real hard.
This was the first draft. In re-writing it, the writers wanted to go for something a little funnier, something that would sound like it was from the family of "flying wedgie," "purple nurple," etc. Someone, I do not remember who, said "Rear Admiral." It sounds real, having the word "rear" in it, but it was manufactured to sound real. As far as we know, it doesn't really exist.
Milhouse: No way, Bart. If I lean over, I leave myself open to wedgies, wet willies, or even the dreaded rear admiral!