Anyone who doesn't read science fiction is leading a stunted existence. (It doesn't have to be mine.)
I'll give you an example: A friend was complaining that she couldn't seem to control her girth.
"Some days, it seems the only exercise I get is hauling my bulk around!" She lamented.
"Yes ..." I sympathized, "but just think how skinny you could be if you only weighed more!"
*Hint: The surface gravity of Neptune is 110% that of Earth.*
Neptune doesn't have a surface. None of the Jovian planets do.
Jupiter and Saturn have an atmosphere containing mostly Hydrogen--as you descend pressure slowly liquefies it and eventually gives the liquefied H metallic properties.
Uranus and Neptune have a mix of Hydrogen, Helium, and methane. Their mantles are water-based.
Pluto doesn't fit into the mix, but still has three moons nonetheless.