American Kirby Is Hardcore: Known as Way of the Meek in Japan. Still referred to as such (well, 'Covenant of the Meek' anyway) in the achievement for discovering them.
Big Damn Heroes: For the Way of Blue Members, coming to their aid when a red phantom Invades the formers world.
Suspiciously Similar Substitute: Their ability to invade sinners is similar to the Blades of the Darkmoon from the first game, without much explanation as to why. The sequel reveals that they're an offshoot of the original Blades of the Darkmoon.
Continuity Nod: They're Dark Souls I's Warriors of Sunlight in all but name, being a co-op oriented covenant worshipping a broken statue and able to whip out lightning-based miracles.
Shock and Awe: Progressing this covenant is required for Sunlight Spear.
Combat Pragmatist: Members will using environmental traps to their advantage against their enemies.
Good Counterpart: Or rather neutral counterpart, of the Gravelord Servants in the first game. Both covenants have the host causing misery for the summoned victim, but the Rat King members are reactionary as opposed to being aggressive.
You Are a Credit to Your Race: The Rat King does not like humans at all, but if you pledge your loyalty to him, he will accept you and reward you for defending the rat nests.
Ax-Crazy: There's nothing preventing you from being invaded by fellow bellkeepers, not even being one yourself.
Recurring Element: More or less 2's response to the Forest Hunters, invading the world of trespassers via a ring at a specific location.
Continuity Nod: The only other covenant to come back with a different name, but the same purpose.