e^x and a constant are out at a party one night, and amidst the drinking and dancing, time gets away on them a little.
To get back to their apartment, they need to cross the park in the wee hours of the morning. But at the edge of the park, the constant spots a sinister figure lurking in the shadows. Peering closer, he gasps in horror.
"It's a differential operator!" he gibbers. "He'll turn me into nothing!" And the constant flees shrieking into the night.
In his drunken state, e^x is on the verge of following his companion... but then stops to think. "Hang on," he says to himself. "I'm the exponential function! A differential operator can't hurt me!" And squaring his shoulders, he strides into the park, right up to where the differential operator is standing.
"Hello," he says cheerfully. "I'm e^x!"
"Why, hello," replies the differential operator, leering. "I'm d/dy..."
-Hyp.