These days, it's pretty well known that the four largest planets in our solar system lack anything resembling "solid ground” in the conventional sense. The gas giants Jupiter and Saturn are primarily composed of a gassy atmosphere, and the ice giants Uranus and Neptune are mostly a mix of semiliquid methane and water misleadingly called "ices". Although they do have outer cores composed of more solid material (surrounding their molten inner cores), they are not stable surfaces but rather sunken gasses that are under so much pressure from the super-thick atmosphere above that they are forcibly compacted into a firm and often superheated mass. Thus, even if you magically bypassed the unimaginably crushing pressure of the atmosphere, you would be landing on more of a slushy expanse of quicksand than a rocky surface. However, this was not widely understood until the mid-twentieth century, which has led some sci-fi authors to speculate that there might be solid ground under the cloud layers which might even support life.
While there are some massive exosolar planets - specifically, the rocky Super-Earths and Mega-Earths - that may be capable of sustaining multicellular life, this trope is specifically concerned with gas giants being depicted as having a surface with native life, or at least one capable of supporting visitors.
A more common, recent adaptation of this trope is having the characters land/live on the rocky moon of a gas giant— indeed the concept of terraformed or habitable moons of surface-less gas planets has become quite popular in media and pop culture, and is more scientifically plausible given the discovery of liquid oceans on Jupiter’s moon Europa. Another common depiction are floating cities in the upper atmosphere of gas giants, as shown by Bespin in The Empire Strikes Back.
If these planets are inhabited, it's Solar System Neighbors. Since these planets tend to have higher gravity than Earth their inhabitants tend to be Heavy Worlders. However, in some works, this aspect may also be ignored outright, and the high gravity not even mentioned. See Once-Green Mars and Venus Is Wet for other discredited models of other planets. For gas giant life that doesn't rely on a solid surface try Living Gasbag or Flying Seafood Special.
- Guardians of the Galaxy (Marvel Presents) depicts Jupiter as having a surface. This is incredibly impossible, so after a few decades, it was changed to mankind having established floating cities on Jupiter, which is also impossible, just not quite as impossible as the previous example.
- Wonder Woman (1942): Neptune evidently has a hard surface and an atmosphere a human can breathe. A few Neptunians try invading earth, only for Wonder Woman to overthrow their dictatorship.
- "Call me Joe", by Poul Anderson, has a traversable Jupiter, except it has no known sapient life. An artificial remotely controlled humanoid is sent to conduct scientific research under the conditions. At one point it is remarked the situation shouldn't exist according to what is known, and no one is certain what the reason is; enough asteroids pulled in to form a solid surface, or a more fundamental error.
- Captain Underpants: At the end of The Adventures of Super Diaper Baby, Super Diaper Baby and Diaper Dog get rid of the evil Deputy Doo-Doo by tying him in toilet paper and marooning him on Uranus, which is completely solid (and much smaller).
- In "A Conquest of Two Worlds", a Edmond Hamilton short story, one of the titular worlds is Jupiter, with a solid surface and humanoid natives.
- In the Hyperborean Cycle by Clark Ashton Smith, Saturn has an ashy surface, liquid metal lakes, and a wide variety of alien inhabitants. Human visitors in the 1932 short story "The Door to Saturn" find it perfectly hospitable and end up living there.
- John Carter of Mars: In the unfinished final book, Skeleton Men of Jupiter, John Carter is taken from Mars to Jupiter. Like Mars, the planet is depicted with a solid surface that even has forests and water, and is inhabited by two sentient races.
- Last and First Men: The Ninth Men are designed to colonize Neptune after the Sixth-Eighth Men's homeworld of terraformed Venus becomes too hot to support life. Despite their Heavy Worlder physiology Nineth Man society collapses quickly but eventually a succession of eight other sapient species evolve from their descendants on Neptune, and the Eighteenth Men are mentioned to use Jupiter and Saturn as agricultural colonies.
- Micromégas has a humanoid native of Saturn as one of the characters.
- Not Final! by Isaac Asimov. Jupiter has, beneath miles of increasingly thick atmosphere, a solid surface inhabited by a xenophobic alien race who set out to exterminate humanity when they make radio contact with a colony on Ganymede. In the sequel Victory Unintentional a trio of heavily overengineered robots are sent down to Jupiter's surface to ascertain the Jovians' technology, it's under a million Earth atmospheres of pressure at a temperature of -70 degrees Celsius. Neither the environments nor the Jovians' heat rays phase the robots in the slightest, and the Jovians surrender thinking they were humans.
- Ricky Ricotta's Mighty Robot: All of the gas giants are depicted as having surfaces and life — the Jurassic Jackrabbits from Jupiter, the Stupid Stinkbugs from Saturn, the Uranium Unicorns from Uranus, and the Naughty Nightcrawlers from Neptune.
- All the planets of the Solar System are habitable in the Captain Future books, including gas giants (and moons too small to hold atmosphere, but that's a different trope).
- In the Clifford Simak short story, "Desertion" (found in City), Jupiter is a solid planet covered by howling winds. Humans have be transformed into Jovian lifeforms in order to go outside. And once they do, they never come back...
- Philip K. Dick sometimes references colonies on Jupiter, Uranus, and Neptune, implying that they are similar to bases on Luna (the Moon) and Mars.
- From Robert A. Heinlein:
- Strongly implied in Tunnel in the Sky, which refers to the "steel-limbed Jovians" who "enjoy gravity 2.5 times ours" and "poisonous air at inhuman pressure".
- "Jovians" are also mentioned in "—We Also Walk Dogs". Neither they nor their homeworld are directly described, but they are described as requiring a high-gravity environment to be comfortable (provided by a centrifuge—or using artificial gravity), but their "apartments" otherwise seem to be rooms with floors and so on, not some kind of tank for living gasbags.
- There's a quick mention of "the stations we now have on Pluto, Neptune, and Titan" in Beyond This Horizon. Well, two out of threenote ain't bad!
- In They Fly So High by Ross Rocklynne (Amazing Stories June 1952), two men Abandon Ship over Jupiter and are caught in its gravity well. Their pressure-suits with Artificial Gravity protect them as they're falling into the gas giant, until they land on a surface of a strange liquid made solid by surface tension. It's also stated there's a Domed City somewhere near the Great Red Spot.
- A Muppet Babies storybook about the title babies imagining themselves participating in a race for some reason depicted Neptune as having a solid surface.
- Dungeon Magazine issue #101 had "Iron Lords of Jupiter", a setting for d20 Modern that was a Genre Throwback to John Carter of Mars-style Planetary Romances set on the rocky surface of Jupiter that lay at the core of its enormous atmosphere.
- Urban Jungle: The "Astounding Science" supplement has life on all four giant planets, in homage to its serial and pulp inspirations. Jupiter and Uranus have solid ground beneath their clouds, inhabited by hexapedal felines and silicoid armadillos respectively. While Neptune is a water world with shark people. Saturn might actually be a gas giant but the rings have an envelope of breathable air and dragon-like residents flying between the ice chunks.
- In Blast Corps, one of the levels takes place on Neptune. It's a "racecourse"-type level where you drive around a rocky track on the surface of the planet.
- Endless Space: Gas giants can be colonized after researching the appropriate technology. The changes to the gas giants' graphics when they're colonized make it clear that the colonies are on the surface of the gas giant and not orbiting habitats.
- Futurama: The frigging SUN (which is actually a star, but Tropes Are Flexible) is inhabited!
- Kerbal Space Program: Early builds included the ability to land on Jool, the fictional solar system's only gas giant. The "surface" was simply a way for the developers to texture the planet without having to drastically change its code in comparison to other planets. Getting there would even reward the player unique messages from the scientific equipment lampshading the absurdity of the situation, and, of course, the treat of wandering around a featureless green plain. Subsequent versions eventually made it so any spacecraft would explode under the pressure if they tried to enter Jool’s atmosphere. Even if they somehow make it through, the "surface" has been removed altogether so there isn’t anything to land on.
- Averted in Starbound; you can try, but you'll just get a message from your navigation unit telling you that it's not possible. Not that it hasn't stopped some enterprising modders from trying...
- In Sol Cresta, every planet you visit is shown as having a solid surface, including Neptune, Uranus, and Saturn. Same with the Sun, as well.
- StarFlight: You can try to land on gas giants, but your ship will immediately be crushed by their strong gravity before you can touch down.
- In Stellaris, one possible scientific anomaly reveals that what your explorers assumed was a gas giant is in fact a rocky, barren world with unusually thick cloud cover. Your astronomers are noted to be deeply embarrassed by the mistake. This could even happen in the Sol System, back before an update that made it so your home system's planets are all automatically surveyed at the game's start.
- In Warframe, most of Neptune's mission nodes are Corpus buildings on top of icy mountains, similar to those seen on Venus and Pluto. No particular explanation is given as to how or why this is the case, though some of the nodes might in fact be on Neptunian moons. Uranus is also depicted as having a massive ocean under its clouds, though Saturn and Jupiter's mission nodes take place on asteroids (presumably in the rings) and floating artificial platforms, respectively.
- The Fairly OddParents!: Jupiter is seen in "Love Triangle", where it's depicted as a rocky, brown surface with mountains. There's even life on it, in the form of a giant, blue cyclops alien.
- Futurama: In "A Tale of Two Santas", the Planet Express crew visits the north pole of Neptune to deliver letters to Robot Santa. It's shown to have a breathable atmosphere, covered in solid ice, and inhabited by four-armed Neptunians and Yetis.
- I Am Weasel: The titular character earned a statue for being the first being that landed on Mars, Jupiter, and Uranus, despite the latter two being a gas giant and an ice giant respectively.
- Looney Tunes: In the short "Jumpin' Jupiter", Porky Pig and Sylvester are abducted by an alien from Jupiter, and by the end, the pair end up on the surface of what is most likely Jupiter.
- When Oscar's Orchestra journeys to space in "Star Tours", the instruments are able to land on Jupiter's surface, and even find that it's inhabited.
- SpongeBob SquarePants: In "Mooncation", Sandy briefly slides across the rings of Saturn as if they were ice.
- The Fangface episode "Dr. Lupiter and the Thing from Jupiter" opens with a rocket ship landing on the surface of Jupiter.
- One episode of Super Friends had them strolling on Saturn, with Batman Can Breathe in Space in effect as well.