Most Star Wars fanatics probably already know about the clip below. In a nutshell, the scene is from A New Hope. Luke, Han, Chewie, and the droids are in the hangar control room on the Death Star, and Obi Wan has just left to shut down the tractor beam.
In the finished film, Chewbacca howls and Han agrees with him. But in this clip, we hear Peter Mayhew saying an actual line of English dialogue, not the familiar "RRRAAARGGGHHH!". Here's the dialogue:
CHEWBACCA: That old man is mad!
HAN: Boy, you said it, Chewie. Where did you dig up that old fossil [Luke]?
Peter Mayhew recently shared another video in which Chewbacca speaks English. It is from The Empire Strikes Back, specifically the first hangar scene on Hoth.
Chewie is working on the hull of the Millennium Falcon when Han approaches. The dialogue is as follows:
CHEWBACCA: What? What? Where the hell have you been? Where the hell have you been?
HAN: Alright, don't lose your temper! I'll come right back and give you a hand.
CHEWBACCA: Where are you going?
HAN: To make my report.
CHEWBACCA: Tell them we're leaving, then!
In the "making of" featurette, Lucas is very clear in saying that, like the guy in the Vader suit, Peter Mayhew had actual lines, and actually said them in English, for the sake of pacing and tone, and to give the other actors something to respond to.
Has anyone come across additional footage, or even a script, that lays out Chewbacca's dialogue in the original trilogy?