I think the legality of drawing Wacky characters is like any other re-creation. As long as you're selling the original drawing it's legal. As soon as you reprint it, copyright law steps in. I could legally repaint Ajerx 100 times and sell them as long as I don't publish them.
Plan,
This certainly seems to be the way things are treated. Go to any comic convention and folks are doing sketches of characters owned by Marvel and DC, and some have even gone so far as to do cover re-creations. That said, I'd GUESS that under the law, Marvel or DC or any rights holder could technically swoop down and stop people from making money using their property.
The way it's typically treated (meaning, no one seems to care) would make one think it falls under fair use... but under the law I'll bet once it's on paper, and you've sold it to someone else, you've TECHNICALLY crossed the line. Or maybe it's like a cover band and a live performance. Though, unlike a drawing, a live performance is temporary... a drawing is not.
Not that it really matters, as whether it's technically legal or not - no one is going to go after Jay or any other artist, for selling drawings of whatever they like. Still, I'd be curious to know how the law defines these things.