Sometimes its not the clients that are the problem:
Many years ago I was working as a trainee programmer while finishing my university degree. After about 6 months on the job I was given the job of updating the intranet home page. I was ecstatic this was amazing me a trainee getting to update the intranet homepage! Something 3000+ employees see on a daily basis! Wow!
I decided that this was my moment I had to mark this occasion forever! I decided I must put an Easter egg on the page. (basically a hidden bit of code that has no purpose other than the programmer showing off and having fun, there are lots hidden in very popular applications just search Google!)
About 10 minutes later while halfway through a sandwich a rather stressed looking sysadmin came running in to the canteen looking for me. "We have a problem, 2000 machines have crashed in the last 5 minutes" At this point Im like F****!!!!! What have I done? We ran back in to the office and everyone is running around like mad its a total war zone! Everyone is panicking phones are ringing like mad! Turns out that lots of machines where crashing when you open the intranet homepage and leave it open for a minute or more.
Knowing that Id just updated the page they wanted to know did I know what might be the problem. I put on my best poker face and said "no but Ill go have a look".
Rushed back to my PC removed the code and re-published the page. I then told the sysadmin guys Ive made an update let me know if things are better. I probably should have waited longer than 5 minutes before fixing the issue as they started pestering me how I managed to fix it so quick.
For fear of my job I kept my mouth shut for the next few months and I eventually confessed to a co-worker who quickly told all the other programmers completely destroying my programming credibility for the next 7 years. Sigh.