The other day I was helping a co-worker set up Ubuntu in VirtualBox, to simulate the production servers. At one point, I told him to search for a package by typing "apt dash cache space search space dash n space ..."
He types it in and says, it didn't work. I walk over to check his display. He's written "apt-gash search -n ..."
I say "You didn't take pre-med in college, you studied CS! It's apt-cache, not apt-gash!" He didn't understand what I meant.
So he corrects it, and types in "apt-cash search -n ..."