In the wig shop, a wig of Fry's, of Futurama, hair can be seen on the top shelf.
The title of the episode is pun on title of the book "for whom the bell tolls" by Ernest Hemingway.
When draining the blood from Elfo they attach a device to his feet and roll them up. It's based on a device used to roll up a tube of toothpaste.