Currently, in my calculus class, I'm covering integration techniques. Now, there are techniques that are, so to speak, broad-spectrum, like substitution or integration by parts; they can be brought to bear in a wide variety of situations. But there are other techniques that are more restricted; some, in fact, that work in only one situation, or an extremely restricted set.
I was outlining one such technique today. (If you're curious, it's the one for integrating e^x sin x.) I pointed out that the trick used works only for the one situation. (Well, you can insert constant factors into various points, but it's really just the one.) Then I said, "You might say that it's a one-pony trick."
Pause.
Dead silence.
I turned around and gazed at them for a moment. "Have any of you ever heard the expression, 'one-trick pony'?"
Dead silence. Not one hand rose.
Ne-e-ever mind...