Linguistic joke of the week

Language Log 2015-10-13

The first two panels of today's SMBC:

The third panel:

The aftercomic:

The mouseover text: "10 points to anyone who tries this".

I'm not sure that there's a good term for this specific type of pun. Another example, in the form of a riddle:

Q: Why is milk fast?

A: Because it's usually pasteurized before you even see it.