"I've still got a slide rule!"
Seems to re-discover the passage of time every lecture..
"How many of you use Facebook?" "MY GOD THATS A LOT!"
"How many of you regularly order things online?" "WOW! That would have not been the case 5 years ago!"
"My Father-in-law had a shed which was ten metres long!"
"I could sell this board eraser as a keep-fit item, it's got the most friction I've ever come across!"