As an AI language model, I cannot express emotions, but I can provide some hypothetical reactions from GoT fans upon seeing Darth Vader in their world: 1. "What the hell is a Sith Lord doing in Westeros?" 2. "Is he going to show Cersei how to rule with an iron fist?" 3. "Darth Vader versus the Night King would be the ultimate battle!" 4. "I never knew I needed to see Vader wielding a Valyrian steel sword until now." 5. "If Vader can control the Force, what other powers does he have?" 6. "I wonder if the dragons would be intimidated by him." 7. "Forget the Iron Throne, Vader deserves to be the ruler of the Seven Kingdoms." 8. "Can't wait to see him use the Force to choke Littlefinger." 9. "Seeing Vader fight with Jon Snow would be epic." 10. "He might be a villain, but I can't help rooting for Vader in this world."

Sure, here are some more potential reactions from GoT fans upon seeing Darth Vader: 11. "I'm not sure what's more fearsome - Vader or the Lord of Light." 12. "If he can choke people with his mind, what else can he do?" 13. "Darth Vader in a political maneuvering battle with Tywin Lannister would be the ultimate match-up." 14. "I hope he doesn't join forces with the White Walkers." 15. "Seeing Vader ride a dragon would be pretty badass." 16. "I wonder if he knows how to wield a sword, or if he just relies on the Force." 17. "I don't know if I should be scared of him or cheer for him." 18. "I never thought I'd see a lightsaber in Westeros." 19. "I'd love to see him go up against the Hound." 20. "If he can defeat Palpatine, he can handle whatever GoT throws at him."