Title text: [title-text similarly alphabetized]
An epigram is a brief, interesting, usually memorable and sometimes surprising or satirical statement.
Just in case you have been living under a rock for the last several years, Twitter is a short message social network / communication service. All messages (known as tweets) on the service need to be under 140 characters, including private messages.
All the words spoken by the woman, from Yeah to Alphabetization are in reverse alphabetical order. They also have 120 characters so would be a valid tweet — hence the joke, and hence "whoa"...
And so is "Title-text similarly alphabetized". Backwards-alphabetized, that is.
[A man sits at his computer desk, motioning toward the screen as a woman stands behind him.]
Man: I don't get why authors and comedians spend so much energy trying to be clever on Twitter. Couldn't they put that creativity into more books and scripts? -- Is there something they like about the 140-character format?
[Same picture, only the man has his arm down.]
Woman: Yeah. Writers working under tight restrictions produce novel material -- like, for example, epigrams employing backward alphabetization.
[The man remains at his computer desk. The woman is no longer in the frame.]
Man: ...whoa.add a comment! ⋅ refresh comments!