The 5th dimension is an alternate universe which is the home to a species of Imps, notably the notorious Mr. Mxyzptlk. Every three months he leaves this dimension and comes to the 3rd Dimension to wreak havoc. But as long as he is tricked into saying his name backward he will be banished for another three months in the 5th dimension.
Planets within the 5th dimension
- The Phantom Zone is also considered a 5th dimension. It seems plausible that there could be more than one 5th dimension, as there are also a number of universes that could also all be considered 3 dimensional, such as Earth-1A, Earth-2A, the Universe of Evil, and others.