Spare Blood

When a person is a member of a company, group, or in a relationship solely to fill the open vacancy; as if the only benefit they bring is blood for donation.

"You're not my friend, you're my bodyguard, make it past two weeks, I might learn your name, until then, you're spare blood." -Alucard, Hellsing Ultimate Abridged, episode 3.

"Andrew is our 'social media intern,' he can make copies or coffee, other than that, he's spare blood.