I'm Here Because You Broke Something
You know what prompted this shirt. One too many incredulous "What are you still doing here?" (emphasis on word of choice, all equally annoying) from the boss. Here's the mental conversation you get to have at that moment: "Oh wait. I know what I'm still doing here. I'm fixing the stuff you so graciously broke earlier today." Unfortunately, you mumble your actual response or couch it in technical jargon that's beyond the INT of those who ask this question so that they cannot not comprehend that it is because of them that you are still here.
When you're sick of that, you're ready for this shirt. Generally the phrase "Well, you'd better go home soon!" can put us right over that edge. We recommend you keep this shirt at your desk to change into at 2 a.m. so that when your coworkers start showing up at 8, you're wearing a different, fresh (and yet entirely applicable) shirt.