Here's the Stupid Professor Trick of the year. Apparently, not knowing how to turn off the external monitor can have serious consequences.
While his students were watching a movie on three screens, Suffolk University professor Luis Garciahe was busily watching porn on his laptop. Unfortunately for him, he didn't realize that he was also projecting it onto the big screen. But luckily for him (if not for his students) he's tenured, so he'll probably keep his job.
Of course, he was "just doing research for a later class module." Yep.
Supposedly, the class continued for 30 minutes after the incident, and none of the students mentioned it to Garcia. So, he remained blissfully unaware of what he'd done until one of the students reported it to the administration. I know that part couldn't have happened at my school, because I doubt my students could gone that long in class before asking "Will this be on the exam?"
Bugs Bunny has some thoughts on the matter, here, and Mike Munger has some further observations here, along with a link to a funny-but-not-work-safe video clip that I wish I'd thought about linking to.