People who call a business on at 7pm on a Friday (and ESPECIALLY on Christmas Eve), get an answering service, and then act shocked (SHOCKED!) that the business is closed. Extra credit when the business you're calling is a doctor's office. Super bonus points if you curse out the operator and call them every name you can think of because you couldn't be bothered to call during business hours and now have to wait until Monday for a resolution to whatever minor problem it is that you have.
Related: people who order a Christmas gift for their child on the evening of December 23rd, having it explained to them that, short of the Doctor stopping by in the TARDIS, there's no way they're gonna have it by Christmas, then calling up on Christmas Eve to find out why their package didn't arrive and telling me how I "ruined Christmas" for their child. And then having to offer my most sincere and heartfelt apologies and sympathize with them about the problem that they, themselves, caused instead of being able to say, "Well, what the hell did you think would happen, especially when we told you there was no way it would even ship out until today? Did you think we'd just hop in the DeLorean and go back to last week and ship your order to you?"