What's Your Favorite Story That Started As A Joke And Became Serious?

Sometimes the coolest ideas start out as just satire, or a prank, and then grow more serious. Case in point: Judge Dredd (pictured above) started out as a straight-up satire on authoritarianism. But what's your favorite joke or spoof that evolved into something serious?

Please include a picture or clip (or book cover, or comics panel) for your chosen story or character. And please mention why they started out as humor, but got more serious (or more broad based) over time. Thanks!

Top image: Judge Dredd cover art by Alex Ronald.