generation gape
(v.) -- to gaze stupidly or in open-mouthed surprise or wonder at someone from another generation for doing or saying something completely surprising or incomprehensible due to the generation gap.
"Whenever I say something old-fashioned to my teenage sons, they just look at me in a totally befuddled way and then generation gape at me in wide-eyed wonder. 'Oh Dad, please!' is what they are thinking, I'm sure!"