According to one of my co-workers, my face turns red and the temperature in the room drops by 10 degrees as soon as I start talking to Captain Useless when he visits my lab.
In my defense, he really should know the material I explained to him five separate times today. In fact, he was the TA for the course where I learned that material. I've tried getting him to repeat back to me what I just said, asked him questions about what I've told him to make sure he understands... but somehow 15 minutes later he always comes back with the exact same questions. It feels like he just doesn't care enough to bother remembering. This also pissed me off because he later brought them up at a group meeting with our supervisors, which wasted the short meeting time we had, especially when they said exactly what I said, along with a, "You should know this." It also kind of made us look really stupid. Like, "We should take less data readings to get rid of the noise." stupid. Aaaaagh. I spent my entire morning explaining these things so that maybe we wouldn't look like fools at the group meeting!