Who is always 100% happy about their jobs? No one can say they're their absolute best every single day. We all make mistakes (pobody is nerfect, wise people would say). The problem is that while some mistakes can be easily mended before the boss notices them, other last through time.
Whether because someone took a picture to share online or they're really impossible to correct, some of our fails will haunt us forever (and others, too. Let's not forget a lot of the things we're bad at affect others!)
There are cases these errors are so big we can't believe whoever made them is totally innocent. Maybe they didn't get if they got fired (maybe they were trying to get fired) or wanted to pull a prank on their customers/managers/coworkers. See these particularly funny fails and judge by yourself: were they or were they not intentional? Have fun!