It appears in the theme song and also during the openings and closings of many episodes. It plays an important role in "Pressure" and "Whale Watching."
It appears as a small island with sand in the middle of the ocean. Its most notable landmarks are the three palm trees that inhabit one side of the island. It appears small, but in reality, it is much larger and appears small because of an optical illusion.
On the other side of the island, there is a forest filled with an array of wildlife and a skeleton who previously guarded the Magic Book.
Bikini Atoll has been around for millennia. The trees that inhabit the island have had its ancestors during the times of prehistory.
At one point, Davy Jones was either on the island or at least had the Magic Book, which previously resided on the island.
After Sandy is frightened by SpongeBob and Patrick (as ghosts), she leaves Bikini Bottom and travels back to Texas via an acorn-shaped rocket, which launches out of the ocean and to the landmark of Austin, Texas.
In the second level, Plankton and Jimmy Neutron have the chance to enter a pipe, which leads to Bikini Atoll. A Krabby Patty cheat trophy is on the island.
In "The String," the island was destroyed when SpongeBob unraveled all of Bikini Bottom and the Milky Way with the string.
The episode "Mrs. Puff, You're Fired" includes the footage from "No Weenies Allowed" where SpongeBob is flung out of the water and back in again.
In real life, Bikini Atoll was used for nuclear bomb testing in the 40s and 50s.
Tom Kenny once debunked a popular fan-theory that said the anthropomorphism of Bikini Botton was a result of the nuclear testing.
Starting with "Lame and Fortune," a CGI model of the island is used instead of the filmed island.
This is because the original model island has not aged well as confirmed by Vincent Waller on Twitter. It is currently buried somewhere deep within Stephen Hillenburg's garage.
When the island is shown at night, a human finger is visible in the water to portray a reflection of the moon. According to the "Christmas Who?" audio commentary, Stephen Hillenburg filmed the Bikini Atoll island at Steve Belfer's house in Tom Kenny's pool in California.