Easter eggs are intentional hidden features.
Floating or Sinking City
A city can float or sink when the tiles on its bottom-left and bottom-right are tapped alternatingly. Tapping on the bottom-left first causes the city to rise into the sky; tapping on the bottom-right first causes the city to sink into the ground. This change is purely cosmetic and does not prevent the city from being attacked or sieged. The change can be reverted by training a unit from the city or ending the turn.
Luxidoor Easter Egg
Before the Moonrise update, Luxidoor could be force-spawned by disabling all other tribes.
In the Steam version, this Easter egg is extended to all unowned tribes.
Mixed Tribes Easter Egg
The Mixed Tribes Easter egg allows players to combine two tribes with three stars each in the tribe selection screen by holding on the icons for two tribes simultaneously on mobile or holding down the alt key and clicking on one tribe's icon, then holding on another's on Steam.
High scores for mixed tribes are saved in the Throne Room.
Mixed tribes have the gameplay features of the tribe selected second and some of the aesthetics of the tribe selected first. Specifically, the first tribe selected determines the first four characters of the name, the city style, and the unit style of the mixed tribe, while the second tribe selected determines the last three characters of the name, the terrain style, and the technology (including starting and special technology, where applicable) of the mixed tribe.
The Nature Bunny is an unit that can be spawned in single-player by tapping an unoccupied tile in player-controlled territory ten times. The Nature Bunny has the crush skill, allowing it to destroy any building on any tile it moves to.
The sunrise Easter egg allows players to change the sky to a pinkish-yellow "sunrise" color by holding the starry night sky background for 15 seconds, then releasing. This change can be reverted by holding the background for 15 seconds again or by relaunching the game.