This is curious indeed! I have never heard the versions of the song y'all are giving. The version I know has these two verses:

I have a horse I call Napoleon he's not fast and he's not smart. Once he made me lose my savings, now he can pull my apple cart.

I have a horse I call Napoleon we met a girl on the Avenue. He kept still when I said let's marry that's how I met my Waterloo.

I think there are other verses, but I can't remember them.