process
Explanation
The Joke
A person asks a cartoonist what the secret to becoming a cartoonist is. The cartoonist gives the standard inspirational advice: "Practice, practice, practice. Learn things. Maybe travel. Be interesting. But mostly, it's about practice." The person thanks the cartoonist, and as they walk away, they encounter something weird: a genie-like creature living on their palm that says "Feed me and I shall reward you." The person then goes to what appears to be some sort of bizarre, Lovecraftian art class where a creature is posing, and is told, "Do you know how gills are different from people?" This is capped by the person saying "Thank you, master."
The joke is that the "secret" to becoming a cartoonist like Zach Weinersmith isn't actually the trite, generic advice about practice and travel. The real secret is having a deeply weird and surreal imagination that generates the kind of bizarre, non sequitur scenarios that fill SMBC comics. The cartoonist's conventional advice is immediately undercut by the utterly strange sequence of events that follows, which is far more representative of the actual creative process behind the comic.
The Humor
The humor works on a meta level: SMBC is famous for its weird premises, absurdist tangents, and surreal imagery. By having the cartoonist character give boring, standard advice while the actual comic itself demonstrates the real ingredient (pure, unfiltered weirdness), Weinersmith is poking fun at the gap between what artists say about their process and what actually goes on in their heads. The escalating bizarreness of each panel after the advice -- a palm creature, an alien anatomy class -- serves as the real answer to the question.