Jabba the Hutt

Marvel Comics were tasked with making a Star Wars comic based on Star Wars: A New Hope... before the movie came out. Because the comic was based on an early draft of the movie, there were differences between the comic and the final cut of the movie. One of the big difference was Jabba Hutt, who made his first appearance in the comic.
Overview
In the draft that Marvel got, Jabba makes an appearance. The scene was removed from the movie due to budget restraints. However, the scene was restored in several re-edited versions. In the actual comic, Jabba confronted Han Solo for killing Greedo and the debt he owed him. However, Solo managed to talk his way out of it by promising to let Jabba take a chunk of the pay for his next job. Pleased by this, Jabba and his gang left. Oddly, "Hutt" was spelt with only one "t" in this.
Due to delays with Star Wars Episode V: The Empire Strikes Back, Marvel Comics were forced to off script for their monthly Star Wars comic and make up their own stories. Jabba appears in these stories. Jabba manged to track down Han and Chewbacca, because they used an old hiding place. Circumstances caused Jabba to remove the Chewbacca and Solo's bounty. This allowed the duo to return to Tatoonie and team up with Luke Skywalker. However, Solo later killed Jabba's employee Crimson Jack (a space pirate), which led Jabba to renew the bounty for Solo. After learning about the reward from a bounty hunter, Solo and Chewy rejoined the rebels. An early scene in Star Wars Episode V: The Empire Strikes Back mentioned the bounty hunter.
Appearance

Jabba the Hutt was a tall humanoid with a walrus-esque face. He wore a bright uniform and a topknot. The reason for the difference in appearance was because the script didn't give a description of how Jabba or his species looked. As such, the creators based Jabba's appearance on an alien that was briefly seen in the Mos Eisley cantina called Mosep Binneed.
References:
https://en.wikipedia.org/wiki/Jabba_the_Hutt
http://starwars.wikia.com/wiki/Docking_Bay_94