Yesterday I was following a suspect when suddenly he turned around to face me and asked "Why are you following me?". I was, of course, taken completely by surprise. "Holy shit, you mean I'm not invisible?"
I whip out my communicator and say "Spock, what the hell happened to my personal cloaking device? Spock? Spock? Damn."
I turn back to the suspect but he's snuck off to get a police officer who, after much debate, is coming over to me to take me to the crazy-person ward.
"Beam me up, Mr. Scott!", I shout. "Dammit, get me out of here!" Luckily, just as the police officer gets to me the communicator starts working and I'm beamed up.
A couple seconds longer and I'd have a hell of a time trying to convince them that I'm sane. Dammit Jim, I'm a Doctor, not a very good actor!