"We're connected. No you, no me. Two sides of the same coin."
—Dark Pit, Kid Icarus: Uprising
For these men, Rapture has no walls. We must find a method of conditioning them against abandonment of the Little Sisters. Something physical... possibly even lethal. The lab aides are starting to call them "Big Daddies." Perhaps there's some genius to that: bonded pairs, connected by a love that kills.
—Gilbert Alexander, Bioshock 2