Minecraft wiki entry for Easter_eggs, associated text: Showing the modified menu screen. Note that the text reads "Play World" and "Reset World".
Banners, obsidian boat, normal boat, and diamond heart.
An explosion of heart particles from an end crystal.
Zombie pigmen wielding heart swords.
Dungeons were replaced with "houses".
The pink wither returns.
The "Minescreeper" minigame.
The hidden QR code.