The fortune cookie is "Who's the more foolish, the fool or the fool who follows him?" which Obi-Wan says in A New Hope [1:07:29].
1:31 and 4:31 - C-3PO (to R2): "Did you hear that?" He also asks him this in A New Hope [2:47]. The first instance in this episode occurs while they're going down the hallway and the ship is under attack, and these circumstances also mirror those in A New Hope.
2:55 - C-3PO: "R2, do something! Get us out of here!" Han Solo also says this to Chewbacca in A New Hope: "Chewie, get us outta here!" [55:26].
6:25 - The Big Hay-Zu: "So, you are the intruders."
C-3PO: "Intruders, oh, hardly, your worshipfulness."
Han calls Leia "worshipfulness" in A New Hope ("Look, your worshipfulness, let's get one thing straight: I take orders from just one person: me!" [1:26:04]), and C-3PO calls Jabba "worshipfulness" in Return of the Jedi ("I am here, your worshipfulness" [15:02]).
9:36 - C-3PO (in response to R2's beeps): "I heartily agree." He uses the same expression in A New Hope after Luke suggests he wait outside by the speeder and says they want to avoid trouble in the cantina: "I heartily agree with you, sir" [45:45].
15:43 - C-3PO: "It's all your fault, R2, all your fault." He places the blame on R2 twice in A New Hope too: "I don't know what all this trouble is about, but I'm sure it must be your fault" [52:03] and "This is all your fault" [1:36:11] (when 3PO is tangled in wires in the Millennium Falcon). He also blames himself when he thinks that Luke, Leia, Han, and Chewbacca are dying in the trash compactor: "It's all my fault!" [1:24:42].
18:18 - C-3PO: "Goodness gracious me!" He also uses this expression in Return of the Jedi, at the door of Jabba's palace [5:52].
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The pit droids' deception of projecting a hologram image of a leader amid smoke and lightning is similar to what the wizard does in The Wizard of Oz.