Easter Eggs allowed?

[racycle]

Are servers allowed to do easter eggs about other games? , just little spoofs.
Im sure easter eggs relateing to other servers is if you get permission to thare content.

Can anyone fill me in on the limitations of it? no easter egg gfx will be copyed from another game , just remade to look like a senero from another.

A example would be , a "error" in the design of a server and players can get around something that seams like they shouldnt. Lets just say they get around and find a level that looks like a populer zelda level just in ruins. but the tileset is different and the name of the area is something simuler like "Glitch to the Past". Would this be allowed? Its simuler to somethign everyone knows, but still not copying right?