A young sarlacc hailing from the Outer Rim planet of I'vorcia Prime, Simpi's existence began during the Imperial Era. She was under observation by Doctor Genzhor when his assistant, Ooris, turned on him. The smugglers Han Solo and Chewbacca were dispatched to I'vorcia Prime by the collector Dok-Ondar to secure several sarlaccs from the late doctor's collection, but they found themselves in a trap orchestrated by Ooris. Managing to evade the danger, the two smugglers cleverly used Ooris as a lure to successfully capture Simpi. Subsequently, they delivered the creature to Dok-Ondar on the planet Batuu.
In 34 ABY, Kendoh Voss and her Kendoh Gang made an attempt to rob Dok-Ondar, only to be interrupted by a First Order sergeant. To avoid being captured, Voss released Simpi by shattering the sarlacc's containment. Simpi then proceeded to attack the sergeant's stormtroopers, which allowed Voss to make her escape.
During the Imperial Era, Simpi began her life as a young sarlacc inhabiting the Outer Rim planet I'vorcia Prime. She was the subject of study by Doctor Genzhor, considered the foremost sarlacc expert in the galaxy, at a research outpost established within the local nature preserve. Genzhor's life came to an end when he was killed through the treachery of his assistant, Ooris.
Around 5 BBY, the smugglers Han Solo and Chewbacca journeyed to I'vorcia Prime on behalf of the Ithorian collector Dok-Ondar, tasked with acquiring several sarlaccs from Genzhor's collection. Ooris deceived the pair, leading them into a trap where he hoped Simpi and the other sarlaccs would eliminate them. However, the smugglers outsmarted Ooris, using him as bait to capture Simpi and transport her aboard their freighter, the Millennium Falcon. Solo and Chewbacca then delivered Simpi to Dok-Ondar's Den of Antiquities, a shop situated in Black Spire Outpost on the planet Batuu. Dok-Ondar housed the sarlacc in a dirt-filled enclosure, putting her on display for his customers. Eventually, the responsibility of maintaining Simpi's terrarium became a chore assigned to the collector's employees.
During the First Order's war against the Resistance in 34 ABY, Vi Moradi, a spy for the Resistance, visited the Ithorian's establishment and noticed Simpi nestled in her tank, partially buried under the sand. Later in that year, following the arrival of the First Order's 709th Legion on Batuu, Dok-Ondar recounted the story of Simpi's capture to the Kendoh Gang as an illustration of his ability to acquire anything, regardless of the danger involved. Despite this warning, Kendoh Voss and her gang later attempted to rob the shopkeeper. However, their plans were foiled when a sergeant from the 709th, along with his stormtroopers, intervened.
Finding herself with no other options, Voss engaged the troopers in combat and, when cornered, shattered Simpi's enclosure. The newly liberated sarlacc promptly began devouring the stormtroopers, creating an opportunity for Voss to escape. After the remaining troopers departed in pursuit of Voss and her accomplices, BK-86, Dok-Ondar's IG-series assassin droid, inquired about eliminating the sarlacc. Dok-Ondar vehemently reminded it of the creature's high cost, assuring the droid that Simpi had gorged itself on the troopers and would be easily returned to another tank.
Shortly after the failed heist, Bina, the Amani proprietor of the nearby Creature Stall, featured Simpi in her interactive book, Bina's Guide to the Creatures of Batuu. Her employees distributed the book to younglings aged nine and under, free of charge. The activity involved the younglings drawing the items that were visibly being digested within Simpi's stomach. Dok-Ondar also began selling a Simpi toy in a new red tank at his Den of Antiquities. In the same year, historian and author Eloc Throno wrote about Simpi in his Batuu guidebook, Traveler's Guide to Batuu, explaining how the locals around Black Spire Outpost viewed her as a point of pride for the community due to Solo and Chewbacca's fame as smugglers across the galaxy. Simpi was also featured in the 907th edition of the Xenobotanical Journal of the University of Coruscant, with an excerpt appearing in the botanical guide "The One With the Green Thumb."
Simpi made her initial, albeit unnamed, appearance in the first issue of the Star Wars: Galaxy's Edge comic miniseries. This issue was penned by Ethan Sacks, illustrated by Will Sliney, and published by Marvel Comics on April 24, 2019. The sarlacc was subsequently mentioned in the D23 article titled "Creatures, Droids, and Aliens: Meet the Fantastical Figures of Star Wars: Galaxy's Edge," released on May 29, 2019. This article showcased the creature's upcoming appearance as an animatronic figure within Dok-Ondar's Den of Antiquities, a retail location within Star Wars: Galaxy's Edge, the themed land that first opened to visitors at Disneyland Park on May 31 of that year.
Simpi received her name through the official lore associated with Dok-Ondar's Den of Antiquities, although initially, the name was only discernable through verbal communication with cast members employed at the store. The name "Simpi" was officially revealed on July 12, 2019, with the publication of the blog post "Cosmic Creatures and Aliens at Star Wars: Galaxy's Edge in Disneyland Park" on the Disney Parks Blog.