Oh, hai - didn’t know this was going on, - I’ll just quote myself from here for some clarification.
To make it easier to see which bits of Star Wars are modelled on Star Wars, consider that Luke and Leia take the “Dorothy” role.
At first, Tattooine is Kansas, and Luke is Dorothy - a wistful orphan who spends his days on the arid, colourless farm of his stolid, plain folk aunt and uncle dreaming of far-off adventure. At the beginning of the action, he is led off the homestead to follow a small runaway creature. Not far from the homestead, he meets a mystic old man, and after a brief exposition, he resolves to return home to his Aunt and Uncle, who need him - however, he immediately finds that he is prevented from returning to the comfort of home by a ruinous catastrophe, and is swept up into the far-off adventure that he had dreamed of.
Later, Leia stands in for Dorothy, as the helpless heroine that needs to be rescued from the fortress of black-robed villain holding her in a cell awaiting execution. As noted upthread, the rescue is effected by our heroes wearing comically ill-fitting uniforms acquired from the guards in an off-screen scuffle.
If you cry foul that we have two distinct Star Wars characters standing in for Dorothy, consider that early drafts had Anakin Starkiller needing rescue from the Death Star - the princess came in a later revision.
To be clear, Lucas “cribbing from” the Wizard of Oz doesn’t mean there’s a 1:1 isomorphic relationship between the two films, just that The Wizard of Oz is one of several elements of the pastiche. There are also references that are just references for the sake of references, such as C3P0 quoting the Wicked Witch of the West’s death throes (“I’m melting, this is your fault!”) after the dogfight with the TIE fighters, or Darth Vader’s puzzled prodding of Obi-Wan’s empty Jedi robe, which references the same scene.