In part 3 of From Star Wars to Jedi: The Making of a Saga, narrator Mark Hamill details the creation of Star Wars: Episode VI Return of the Jedi's giant, slug-like crime lord: Jabba the Hutt.
The early designs for Jabba didn't quite hit the mark. According to George Lucas, the first design was too human; the second was too snail-like; the third was just right. Jabba became the most complex puppet ever constructed for a movie. His head neck accommodated two main puppeteers, while other operators were placed elsewhere in his body; the gangster's eyes and facial muscles were radio-controlled. Stuart Freeborn oversaw the creation of Jabba, who took three months and close to half a million dollars.
Jabba was originally supposed to be in Star Wars: Episode IV A New Hope, and a scene was shot featuring a human male standing in for the role -- as seen in this video. The creature was to be super-imposed, but the sequence was left unfinished. When it came time to use Jabba in Star Wars: Episode VI Return of the Jedi, Lucas took the opportunity to redesign and improve the character.