Lumpy Space is a cloud-like cityscape in another dimension that is home to the Lumpy Space People. The portal to enter Lumpy Space is located in the Cotton Candy Forest, inside of a frog sitting on a mushroom and requires a password. In Volume 5 of the Adventure Time comics, the password is revealed to be "how many beans you have eaten in the past year". A portal is seen in the frog's mouth, and the ones entering are "eaten" by the frog and pulled into Lumpy Space. The frog questioned Lumpy Space Princess about "non-lumpers" entering. It is hinted that there are other entrances to Lumpy Space. Lumpy Space Princess is part of the royal family of Lumpy Space. In Lumpy Space, non-lumpy people are referred to as "smooth," "non-lumpers," or "smoothies."
- Lumpy Space is very vast and lumpy, as indicated by its name. The landscape (land lumps, otherwise known as lumpy clouds) is in various shades of purple and blue. Makeout Point, however, is colored with shades of orange and green. Elm trees are seen in many areas; it is possible that these are the only vegetation in Lumpy Space. Most of the buildings in Lumpy Space are on separate "land lumps," which resemble floating clouds. Lumpy Space People need cars to fly between land lumps, or else they will fall into the Lumpy Abyss. One building, Brad's house, has a waterfall flowing from the house.
- In Adventure Time: Hey Ice King! Why'd you steal our garbage?!!, Lumpy Space Princess temporarily goes insane with rage and threatens the Lumpy Space Reactor Core, which if destroyed would threaten all of Ooo. No further details are given, though Princess Bubblegum mentions how reactor cores predate the Great Mushroom War, implying that perhaps Lumpy Space has a connection to the ante-Mushroom War world.
Since Lumpy Space Princess's parents are shocked at their daughter's use of the word "lump," it is likely considered a swear word in Lumpy Space. The residents of Lumpy Space are seen to have a negative view of outsiders, or "non-lumpers," although there are a few "smooth posers" like Lenny, Glasses, and Monty who hang out at Makeout Point and use the antidote to The Lumps to become temporarily smooth.
The Lumpy Abyss is a bottomless pit introduced in "Trouble in Lumpy Space". An individual has to travel by car in Lumpy Space or fall into the abyss (whether they are Lumpy or non-Lumpy). Finn explained it as a "million-mile fall into space." Monty, Lenny, and Glasses refer to the Lumpy Abyss as an "eternal void." Lumpy Space People can glide over it somewhat, as Finn is able to get from Makeout Point to promcoming by jumping.
Lumpy Space Princess's house
Lumpy Space Princess's house is where Lumpy Space's royalty resides, rather than a castle. It appears to be crooked and distorted. It has a lilac roof, pink walls, blue windows, and trees on its left.
Lumpy Space School
Lumpy Space School first appears in "Trouble in Lumpy Space". It is home to the weekly promcoming and the gathering of Lumpy Space students. At one particular promcoming, Finn and Jake cure themselves of The Lumps. It can be found in the lower corner of Makeout Point.
Makeout Point is a cliff in Lumpy Space "notorious for smooth-posers", and is where Lumpy Space People come to make out. The cliff also has green and orange, unlike all the other bits of land, and has lime-green trees. According to the smooth-posers, they are only there because they were dumped there. It can be viewed from Lumpy Space Princess's house, but the Lumpy Abyss surrounds the bit of land where her house sits. It is seen in the episode "Trouble in Lumpy Space," when Melissa takes Finn and Jake there to get the antidote for The Lumps.
- In Game Creator, the player can choose their background as Lumpy Space.
- The way each "smooth-poser" in Makeout Point enjoys sitting on the antidote to become temporarily smooth may be a subtle drug use reference.
- The word "makeout" was removed from Makeout Point in Cartoon Network Australia.
- It is unknown if Lumps antidote is left there or if it is returned to Makeout Point.
- Lumpy Space Princess is shown to have celebrated her 15th birthday in the Lumpy Space School as seen in "The Eyes."
- Lumpy Space People generally use valspeak and seem to be preoccupied with shallow pursuits such as the attendance of the aforementioned weekly promcoming dance and other such things typically associated with the "valley girl" subculture.
- The portal of Lumpy Space is located in the Candy Kingdom, as shown in "Trouble in Lumpy Space."
- At the end of "Come Along With Me" Lumpy Space Princess is shown becoming the new ruler of Lumpy Space.