One thing that's struck me (having heard the Hair soundtrack album back in the day) about the song 3-5-0-0 (assuming it's in the revival — it was about the Vietnam War, but I recall reading an interview with the writers that they envisioned, as the show's run continued, retconning those bits to refer to the war de jour): the line "electronic data processing" must surely have lost the resonance it had back in 1968, when computers were remote and to many people semi-mythical gadgets. (I was still in school back then, and one kid accused me of "believing in" computers, as if they were some kind of fairytale.) Nowadays it's probably a rare household which doesn't have at least two computers, and that's not even counting all those devices which generally aren't thought of as "computers" (games consoles, TV sets, DVD recorders/players, music players, smartphones...) but which all the same have far more processing power than the PET or XT ever dreamed of.
I'm sure there's a trope for this, which should be added to the article, but I don't know the name or what terms to use to search for it.
The opening of the London (UK) production of Hair was very precisely timed to be one day after the UK theatre censorship law was repealed. Is there a trope for that?