Sea slugs, alternatively written as sea-slugs, were beings that inhabited the oceans. A few decades after 382 BBY, Scalvi individuals named Carli and Tren were engaged in play, acting out a famous encounter that their uncle, Bree Menaren, had with the Crulkon species. Tren, taking on the role of Menaren, mimed stabbing Carli, who was pretending to be a Crulkon, while exclaiming, "Die, Crulkon sea slug!" In 34 ABY, Ace Squadron pilot Hype Fazon likened his fellow pilots to sea slugs, and threatened to abandon the squadron if his squadron leader Jarek Yeager made him continue to collaborate with them.
The Mon Calamari named Rask Odai had an aversion to children, and he compared them unfavorably to sea slugs.
The initial mention of sea slugs within the current Star Wars canon occurred in the episode "Live Fire," which served as the third episode within the second season of the animated television show Star Wars Resistance, initially broadcast on October 20, 2019. Within the Star Wars Legends continuity, the original appearance of sea slugs was in "The Spira Regatta," a roleplaying scenario penned by Paul Sudlow intended for utilization with West End Games' Star Wars: The Roleplaying Game, featured within the first issue of the Star Wars Adventure Journal publication during February 1994. Later, the spelling sea-slug was used for the creature in the "A Buyer's Guide to Alternative Starships" article within the fifth issue of Adventure Journal, authored by Stephen Luminati and released in February 1995.