I once finished a series of spots, and delivered them on Digital Betacam, as it was 2008-9ish…
The week of airing we received Irate calls from the agency producer who berated us for sending Low Quality Masters. After much back and forth, and investigation we came to find that the producer themselves used a compressed file from a post for the masters that aired over TV.
Remember what compression looked like in 2009? LOL
Not an intern mistake, but should have been? smh
#alltoofamiliartous
Unfortunately, my biggest career achievements in terms of work content have all been credited to others.
It’s the worst part of our job, and when you assume the “freelance” title it only gets worse (but well worth the trade off imo).
This isn’t flame related per say, but back when I was first getting started compositing, I was also on dating apps. I was ASTONISHED by the number of colorists on OK Cupid (having just really learned what a colorist did). It was like, I had no idea how many colorists were out there! I subsequently learned, after asking about what projects one of these colorists was working on (if it was long form/ short form, etc) that someone who dyes hair at a salon is also called… a colorist.
Thank you for the literal LOL.
That’s when you break out your Thomas Guide™ 
Not intern but maybe worse I was a bartender in Vegas working the discreet private party during NAB '97 and spilled on a drink on one of Mr. Szalwinski’s colleagues pants 
I should have absolutely known better, and there’s really no excuse for this. Our facility had just doubled in capacity and we were setting up new Flames. I navigated to /mnt/San-01/ and since both mac users and linux users had access to the shared volume, one of the mac based producers created a folder in a job where they were putting extra stuff. It was called etc and there was nothing in it. I knew this was a bad idea, so I navigated to it and typed in rm -rf /etc.
It took a day to recover that machine.
As an intern I delivered some motiongraphic layers and checked them with the flame artist in the suite. Meanwhile I saw some strange looking masks in the mainspot and asked about it. Unfortunately, it was the day of delivery and one client also already had been in the room. So she also wanted to know, why that is in the spot and yes… 
That day I’ve not only learned to shut up when sb. else is in the room, but also, to teach the exact same thing in reverse the first day on.
Wups.