When I was an FO I once flew with this captain who was a real worrier. Fast forward a few months and we had him in the jumpseat. I hadn’t even finished setting up the FMS and he says, “something’s wrong with your fuel there, it says we’re only going to have xxxlbs at destination!” I give him a sideways look and update the total fuel on the perf page. The fueler left maybe 2-3 minutes ago...

Then on the arrival below 10,000’ we got vectors to final. Flying the -900 we’ve got that fancy VNAV to use on OPDs. Well as soon as I spin the heading in we get into the turn this guy keys up to let me know the vnav is still armed... like cmon man give us a second to make sure the airplane is going where I want it to.

I think he got the hint when I shrugged him off, stared at it for a second or two before turning it off. The best part was he said.. “If I see something I’m going to say something... but I’ll shut up now”