For me, it's the whole "What's Opera, Doc?" bit, which I always paired with "Rabbit of Seville." In the "Ride of the Valkyries" spoof, I love when Bugs, in a wig and dressed as a Viking maiden, is at the top of some steps, with Elmer as the Viking below. Elmer sings, "My wuv, you are so beautiful." Bugs answers, "I know, I can't help it." LOL