This phrase probably means something unique, has no similar thing from its sex.
She's not easy to find, she's one of a kind
This is an old use and still use for this catch phrase to tell someone see you. and the answer for it after while, crocodile, alligator and crocodile were brought for the sake of rhyme.
OK, see you later, alligator.
After while, crocodile.
This expression can be used to tell that someone has no money. I am broke there means that there's no money. I have no bones means that there's also no money. Bones means money in American Slang.
I am broke. I have no bones!
Where's the fire? is an expression or a catchphrase said to someone when seeing it hurrying, simply means why hurrying up. (Hurry UP).
Where's the fire? hey man go slow.
this means that bad things or situations always come in groups, they never come in a single way.
A: Guess what?!
A: Last night my car was stolen, anyway, misfortunes never come singly, I lost my wallet today.
sometimes people can express things with their own words, for example, that expression above can be meant, to defecate, when you wanna do this action , you feel that you have something like a load you wanna unload it.
A: I wanna go to the rest room, I wanna unload the load dog!!
insult, considered to be insulting.
Aw, that's a slap on the face.