Home again, home again, jiggety jig

Bonus points if you can tell me where that comes from ;)
Not that it's particularly obscure or anything, so hardly a difficult quiz. Mind you, I was rather shocked to discover recently that one of my gaming group hadn't seen it! We rectified that pretty quickly, although that doesn't change the fact that he hasn't seen Firefly either, which is equally disgraceful!
( The usual waffle, under the cut )