You hand a bank teller an envelope, and when she asks, "What's this?", you realize you just dropped the company's deposit in a mailbox.
A woman comes into the store, you turn to the other salesman and say, "I waited on the last fat ugly old lady. This one's your turn". Your boss is standing behind you. It's his wife.
While your boss is at lunch, you sneak in and look at some confidential information on his computer. You spill coffee on the keyboard. It shorts out.
You return from a week's vacation to find that you had scheduled *this* week as vacation, not last week.
You take a "sick" day. The next morning the boss asks you, "So, how was the fishing on Rock Creek yesterday?".
You wake up hung over. You have a black eye and barked knuckles. You're in jail. Last night was the company Christmas party.