I'm linking the above old xkcd mostly because it's funny, makes a good point which I hadn't given much thought to, and I'd never seen that particular comic (which is especially strange because the one immediately prior to it is pretty well known), but also because I want to criticize it. And I want to criticize it by asking rhetorically if it's any funnier than the following:
A Dialogue on Dreaming
Xerxes: Are you coming to dinner?
Yvonne: Yeah, but first I'm gonna go comatose for a few hours, hallucinate vividly, and then maybe suffer amnesia about the whole experience.
Xerxes: Ok, cool.
I don't really think it loses anything by just being translated into text, which forces one to ask why it's being presented in webcomic form. I also want to add, if it isn't obvious, that this critique does not generalize to all xkcd strips, many of which are essentially visual.