Making of a SpongeBob Cover Part 2 -- Step-by-Step from Sketch to Print

The whole Nick Mag cover process (just like everything else in life) starts with an idea. For this SpongeBob cover, the idea was pretty loose -- just some gag featuring SpongeBob and Patrick blowing bubblegum bubbles. So, how do I come up with a gag when I have just the beginning of an idea? I just start sketching. Even if I don't