Bob --

I only know one, with variant. The short form is:

"We have met the enemy and he is us."

It's attributed to Walt Kelly, and I think Pogo himself is to have said it, and that's the one that I've known for years. But I've never actually seen it written that way in any Pogo strip (I admit that my search has not been all that diligent). What I have found is this longer form, in context:

"There is no need to sally forth, for it remains true that those things which make us human are, curiously enough, always close at hand. Resolve then, that on this very ground, with small flags waving and tinny blasts on tiny trumpets, we shall meet the enemy, and not only may he be ours, he may be us."

        "Forward!"

                                – Walt Kelly, The Pogo Papers

michael