What would you include on a list of things that millennials have probably never heard of and have to look up on the internet?

Yes!
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Wait one cotton-pickin' minute! How do you know about these unless you're older than dirt like some of us?

Lol, I was an 80’s kid, which doesn’t make me older than dirt. It does make me older than the maturity level I display on this site though... ;p 

There's an app for that first one.

I know what a clutch pedal is.  My car's a six speed manual and my pickup truck's a five speed manual.  I also used to drive a truck for a living.  My first employer had 18 speed manuals but my last company had 10 speed automatics but now finding trucking companies that still have manuals is getting harder to do.