Minecraft wiki entry for Easter_eggs, associated text: The translator cape has a big pink T on its underside.
The Chinese translator cape has a small pixelated Chinese flag on its underside.
cheapsh0t's cape has a small pixelated Japanese flag on its underside.
Drullkus' cape has the prismarine block texture as its underside
The Scrolls Champion's cape has an S on its underside.
The turtle cape has the turtle's belly on its underside.
Gr8_Escape's cape has a star on its underside like on Millionth Customer cape.