Bad Physics Joke

Ok, so I print off my Physics homework in order to work on it (imagine that). And here's the first sentence of problem 1:

An electron, a proton, and a photon all have a de Broglie wavelength of 100 nm.

It sounds like the beginning of some very bad joke made by a physicist.... I'm not sure I want to read the rest of the question yet.... Maybe Katya can provide some humorous punch-line, since I have no realistic understanding of what's happening in this class yet.