Fuel in the cranckcase

As long as I'm asking questions...

I remember when i was a kid that the crankcase could sometimes catch fuel from the carbueretor or float bowls or something, and you may think that your car never used a drop of oil, but actually it did. I don't know how true that was.

But what about our deisels? Can fuel get into the cranckcase via leaking injectors (not likely), or perhaps be traded in the IP or at the fuel shut-off diaphram?