I chose one called "Sophie can walk", which I thought was quite funny. And I watched a couple of library ones, but it's getting late, so I haven't got time for any more. Personally, I wouldn't want to spend a lot of (any, actually) time searching through Youtube for one that might be interesting - I prefer my son to tell me about good ones and then I can just watch them.
Yes, I'm sure if someone could make an entertaining one about libraries they could use it as a recruitment tool or something (though I can't quite imagine what they would put in it that would make people leap up out of their seats shouting,"Yes! yes yes yes! I want to be a librarian!")