Parts of speech

what is the plural of Stick-in-the-Mud ?

Is it Sticks -in-the-Mud ?
Or Stick-in-the-Muds ?

Oh no. You mean there's more than one of them?
Well, I'm inclined to say "what a bunch of stick-in-the-muds" because a) it sounds better, and b) the hyphens pulling the words all together to make it into a collective lump. Unlike, for example, Attornies General

It's sisters-in-law. So I would think it is sticks-in-the-mud. But that's just an opinion.

In this case I think that the derivation of the phrase may decide it. Is 'stick' of the wooden variety, or of the getting stuck variety?

Well, if it sticks in the mud it could get stuck a lot. A bunch of sticks in the mud could cause a flat tire too. Those stick in the muds that won't jump from helocopters could be a bunch of sticks in the mud if they do.

I think it has to be "stick-in-the-muds" because "stick" functions as a verb here, not a noun. The noun is "mud." (But I'd prefer "Johnny-come-latelys" to "Johnnys-come-lately," and "lately" isn't a noun. Perhaps another difference is that "stick..." is slang and "sister-in-law" is standard, and so we don't expect the plural of the former to sound correct.) Does it need to be pluralized? Why not say "old fogies" or something else?