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Bernie's Button
Summons a cherished teddy bear 'My childhood buddy - Bernie!'
You're always there for me, Bernie
5what it really costs
The gold price is the easy part. The Princess only moves in once every other town NPC is alive and housed at the same moment, so buying this pet is closer to a receipt for having built a complete town and kept everyone breathing. Plantera has to be down as well, which puts it firmly in the back half of a world.
the reference
Bernie comes from Don't Starve Together, and the flavor text on both the item and the buff borrows the way Willow talks about him over there, including one line written for an event that never shipped in that form. The crossover runs both directions, which is also why Deerclops turns up in your snow biome.